4-CHLOROANILINE

The results of the many Salmonella mutagenicity tests were inconsistent. However, weak mutagenic activity was repeatedly shown in the presence of S9, presumably due to optimized test conditions. Single tests demonstrated the absence of mutagenic activity in the umu-test or in tests with Escherichia coli and the absence of mitotic recombination in Saccharomyces cerevisiae. PCA induced DNA damage in the Pol A test and gene mutations in Aspergillus nidulans. However, several mouse lymphoma assays uniformly found mutagenic activity of PCA in both the presence and absence of metabolic activation. In contrast, test results for the induction of chromosomal aberrations and sister chromatid exchange in Chinese hamster ovary cells as well as for the induction of DNA repair in primary rat hepatocytes again were conflicting for different laboratories. Overall, the screening tests indicate a possibility of mutagenicity.

PCA (14.5 and 19.0 µg/52 000 cells) was evaluated as positive in a cell transformation assay in Rauscher leukaemia virus-infected rat embryo cells measuring acquisition of attachment independence (Traul et al., 1981). Conflicting test results have been reported by one working group on the transforming activity of PCA in Syrian hamster embryo cells in identical test concentrations ranging from 0.01 to 100 µg/ml. In the first detailed publication of test results, no transformed colonies were identified at all (Pienta et al., 1977); in the later publication, however, test results were summarized as positive in the entire concentration range tested (Pienta & Kawalek, 1981). In an interlaboratory evaluation, both laboratories reported PCA as having transforming activity in the C3H/10T½ cell transformation assay in non-cytotoxic concentrations ranging from 0.8 to 100 µg/ml (Dunkel et al., 1988).

8.6.2 In vivo

In a wing somatic mutation and recombination test in Drosophila melanogaster, exposure was by 6-h feeding of 7.84 mmol PCA/litre. PCA was genotoxic in both repair-proficient and repair-defective larvae of the mei-9 cross, which indicates a potential to induce point mutations, chromosome breakages, and mitotic recombina-tions (Graf et al., 1990).

In a micronucleus test in the bone marrow of CFLP mice, the maximum tolerated dose of 180 mg PCA/kg body weight (single dose given by gavage as a suspension in tragacanth) caused no significant elevation of micronuclei in the time range 24–72 h post-administration (BUA, 1995). In another study, B6C3F1 mice were dosed with 0, 25, 50, 100, 200, or 300 mg PCA/kg body weight dissolved in phosphate-buffered saline 3 times at 24-h intervals, and bone marrow was collected 24 h after the third treatment. The micronucleus frequency at the highest dose (300 mg/kg body weight) was significantly increased (P < 0.001) over the corresponding control value.⁷

No studies are available on the reproductive toxicity of PCA, nor were conclusive fertility studies available for aniline.

In an in vitro assay with renal cortical slices from untreated rats, 4-chloroaniline showed a weak nephrotoxic potential. Altered cellular function was inferred from decreased gluconeogenesis (27% with 0.1 mmol PCA/litre and 42% with 0.5–2 mmol PCA/litre), whereas there was obviously no cytotoxic effect (absence of increased lactate dehydrogenase release) (Hong et al., 2000).

An in vitro test system, the migration-inhibition test with sheep peripheral blood lymphocytes, demonstrated the cytotoxic activity of PCA at concentrations ranging from 0.1 to 1 mg/ml and its immunotoxic activity at concentrations ranging from 0.001 to 0.01 mg/ml; the NOEC for immunotoxicity was 0.0001 mg/ml. The immunotoxic effect was detected as a decreased ability of leukocytes to respond to the mitogenic stimulus of lipopolysaccharide (polyclonal activator of B lymphocytes), concanavaline A, and phytohaemagglutinin (polyclonal activators of T lymphocytes) (Kačmár et al., 1995).

The unusual and rare tumours of the spleen induced by rats administered aniline and related compounds have led to studies into the pathogenesis of splenic lesions. Fibrosis of the spleen was seen in all dose groups with PCA. Goodman et al. (1984) proposed that methaemoglobin bound with aniline compounds (e.g., PCA) or their reactive metabolites is broken down in the red pulp of the spleen and the reactive metabolites are released, binding to splenic mesenchymal tissues and resulting in fibrosis, which progresses to the formation of splenic tumours. Bus & Popp (1987) suggested that the splenic tumours are a result of erythrocyte toxicity. The damaged erythrocytes are scavenged by the spleen, where they cause vascular congestion, hyperplasia, fibrosis, and tumours.

Whether the mechanism of carcinogenesis is mediated through genotoxic or non-genotoxic events is unresolved. PCA is genotoxic in vitro but appears to be dependent on metabolism for its full expression. There is one positive study in vivo (micronucleus test), but this was positive only at a dose level in the range of the LD₅₀.

It is suggested that species differences between rats and mice with regard to splenic and liver neoplasms could be due to differences in the metabolism and disposition of PCA. The NTP (1989) report points out that the initial decay constants for PCA clearance from the two strains of mice tested (A/J and Swiss Webster) were 10 times greater than those in mongrel dogs and rats. The PCA clearance in mice was too rapid to permit the calculation of kinetic parameters (Perry et al., 1981).

For aniline, it was found that there was a larger concentration of the putative reactive metabolite N- phenylhydroxylamine in rats than in mice. There were also higher levels of methaemoglobin reductase in mice than in rats.

Confirming the results of animal studies (see section 8.1.2), PCA in humans is a more potent cyanogenic agent than aniline. Dermal absorption plays a predominant role in intoxication (Linch, 1974). Severity of adverse effects may increase with concomitant intake of ethanol (BUA, 1995).

Three cases of severe intoxication have been reported after occupational exposure to PCA (Betke, 1926; Scotti & Tomasini, 1966; Faivre et al., 1971). One of these cases (Betke, 1926) resulted in death. Severe methaemoglobinaemia was reported in all three cases. The fatal case was accidentally sprayed in the face and on the upper part of his clothing with hot PCA. One of the cases (Faivre et al., 1971) handled powdered PCA. The third case (Scotti & Tomasini, 1966) was likewise exposed to dust while grinding PCA.

An insufficiently documented study reported an inhalation exposure to 44 mg PCA/m³ as being "severely toxic" within 1 min, whereas "signs of illness" appeared after prolonged inhalation of 22 mg/m³ (no further information) (Goldblatt, 1955). In one plant, average workplace air concentrations at two sites in PCA production were 58 mg PCA/m³ (range 37–89 mg/m³) and 63 mg PCA/m³ (range 46–70 mg/m³), respectively. Inhalation and simultaneous dermal absorption resulted in cyanosis, increased methaemoglobin and sulfhaemoglobin levels, the development of anaemia (2 of 6 workers within 4 weeks), and acute intoxication (1/6, who had to discontinue working) (Pacséri et al., 1958). In another plant producing PCA from 4-chloronitrobenzene, 14 workers showed a significant fall in haemoglobin and significant increases in methaemoglobin, which did not correlate with the air concentrations of PCA (values not given in study report) (Monsanto, 1986).

For comparison, in otherwise healthy patients, levels of methaemoglobin in excess of 30% may cause fatigue, headache, dyspnoea, nausea, and tachycardia. Lethargy and stupor, as well as deteriorating consciousness, occur as levels approach 55%. Higher levels may cause cardiac arrhythmias, circulatory failure, and neurological depression. Methaemoglobin levels higher than 70% are usually fatal (Coleman & Coleman, 1996).

Cyanosis and methaemoglobinaemia (14.5–43.5% methaemoglobin; normal range <2.3%) in three premature neonates (gestational age 25–27 weeks) were reported to be associated with PCA contamination of the incubators (no information on PCA concentration) in Amsterdam. Exposure was by percutaneous absorption or by inhalation of PCA-containing vapour produced by the inadvertent use of chlorohexidine gluconate (0.25 g/litre) as a humidifying agent, which decomposed on heating to produce PCA (van der Vorst et al., 1990).

A further report describes the same scenario in a neonatal intensive care unit in Copenhagen, showing that premature neonates developed severe methaemoglobinaemia when exposed to even small amounts of PCA formed from the inadvertent use of a 0.02% chlorohexidine solution as a humidifier in new incubators. The authors estimated that the maximum amount of PCA that the neonate could be exposed to was 0.3 mg/day, provided that all PCA produced was absorbed by the neonate. Thirty-three of 415 neonates (8%) were found to be methaemoglobin positive (mean methaemoglobin concentration 19%; range 6.5–45.5%) during the 8-month screening period. Of those patients with a gestational age of less than 31 weeks, 40% were positive; 15 out of 25 neonates (60%) with a birth weight <1000 g proved to be positive. All the methaemoglobin-positive cases started when the neonate was in the new incubator.

A prospective clinical study showed that immaturity, severe illness, the time exposed to PCA, and low concentrations of NADH reductase probably contributed to the condition. Fetal haemoglobin is more easily oxidized than adult haemoglobin; further, the delicate skin of the premature neonate is more permeable (Hjelt et al., 1995).

Data on the metabolism of PCA, biomonitoring of haemoglobin adducts, and urinary excretion of PCA in humans are presented in sections 7.3–7.5.

Numerous tests have been performed on the toxicity of PCA to all trophic levels of aquatic organisms. Experimental test results for the most sensitive species are summarized in Table 10. Additional data on the toxicity of PCA to aquatic organisms are cited in the BUA (1995) report. Acute and long-term tests are available for invertebrates and fish. Among all tested organisms, green algae (Scenedesmus subspicatus) and water fleas (Daphnia magna) proved to be the most sensitive freshwater species in a short-term cell multiplication inhibition test and an immobilization test, respectively. EC₅₀ values of 2.1 mg/litre for Scenedesmus subspicatus and 0.31 mg/litre for Daphnia magna were determined. The test on fluorescence inhibition of Scenedesmus subspicatus, which resulted in the lowest reported EC₁₀, is not considered reliable, as the test method is not validated and the environmental relevance of the results is questionable. In the only available valid long-term test with Daphnia magna, a 21-day NOEC of 0.01 mg/litre was established for reproduction (Kühn et al., 1988, 1989b). The shrimp Crangon septemspinosa was the more sensitive of two tested marine invertebrate species, exhibiting a 96-h lethal threshold concentration of 12.5 mg/litre (McLeese et al., 1979). With respect to freshwater fish, the lowest short-term (96-h) LC₅₀ value of 2.4 mg/litre was determined for the bluegill (Lepomis macrochirus) (Julin & Sanders, 1978). After long-term exposure, a 3-week NOEC of 1.8 mg/litre was reported for zebra fish (Brachydanio rerio) (BUA, 1995).

Table 10: Aquatic toxicity of PCA.

The chronic effects of PCA on growth and reproduction of zebra fish were further studied in a three-generation test (flow-through system). Whereas the F₀ generation remained unaffected by PCA concentrations of 0.04, 0.2, and 1 mg/litre, the F₁ and F₂ generations showed abdominal swelling, spinal deformations, reduced number of eggs, and reduced fertilization from the age of 5 weeks at the exposure concentration of 1 mg/litre (Bresch et al., 1990). In the same tests, Braunbeck et al. (1990) studied the effect of the applied PCA on hepatic cells of zebra fish and additionally exposed rainbow trout (Oncorhynchus mykiss). For both species, exposure to PCA concentrations of 0.2 and 1 mg/litre resulted in significant ultrastructural changes of hepatic cells. In later studies on zebra fish with prolonged exposure (31 days), hepatocytes and gills of exposed fish exhibited dose-dependent alterations at PCA concentrations of >0.05 and >0.5 mg/litre, respectively. Pathological symptoms in both liver and gills disappeared almost completely within a regeneration period of 14 days (Burkhardt-Holm et al., 1999).

Dissolved humic materials in the exposure media may have a marked influence on the toxicity of PCA to aquatic species. Lee et al. (1993) found significantly reduced toxicity for cell multiplication inhibition of Daphnia magna (48-h EC₅₀) with increasing dissolved humic material concentrations, whereas the LC₅₀ for zebra fish remained unaffected in the presence of dissolved humic materials. Among several explanations, the authors discussed reduced bioavailability by sorption of PCA to dissolved humic materials as a possible cause of this effect.

Several experiments have been conducted on the influence of PCA on soil microbial activity. In general, PCA exhibits low toxicity. None of the applied test procedures is validated, and degradation as well as adsorption to soil particles, which may significantly influence bioavailability, were considered in only one of these studies. Therefore, only the results of the latter study are summarized here. Welp & Brümmer (1999) determined effective doses (ED₁₀) in the range of 85–1000 mg/kg for the Fe(III) reduction by the natural microflora in upper soil material (A horizon) of six different soil types. The authors found a close correlation between effect concentrations and the amount of organic carbon, emphasizing the importance of sorption and solubility for the bioavailability of the chemical. They concluded that the variability of the determined effective dose values could mainly be attributed to the differing ability of soil particles to withdraw organic chemicals from the liquid phase via sorption.

The toxicity of PCA to higher plants was tested according to OECD Guideline 208 with oats (Avena sativa) and turnip (Brassica rapa). After exposure of seeds to different test substance concentrations, 14-day EC₅₀ values of 140 mg/kg soil (oats) and 66.5 mg/kg soil (turnip) were determined for reduced fresh weight of grown shoots (Scheunert, 1984).

In a test conducted according to OECD Guideline 207, the adverse effects of PCA on earthworms (Eisenia fetida) were examined by Viswanathan (1984). After exposure in an artificial soil mixture, a 28-day LC₅₀ value of 540 mg/kg dry soil was established. The minimum weight of test animals as prescribed by the guideline was not reached in 32% of the tests, thus leading to a limited validity of the study. Furthermore, the environmental relevance of the earthworm test seems questionable, as the factors determining the bioavailability of the applied chemical remain completely unconsidered.

Valid studies on the toxicity of PCA to terrestrial vertebrates or on its effects on ecosystems are not available.

The results available on microorganisms and plants indicate a low toxicity potential of PCA in the terrestrial environment.

11.1.1 Hazard identification and exposure–response assessment

Repeated exposure to PCA in rodents leads to cyanosis and methaemoglobinaemia, followed by effects in blood, liver, spleen, and kidneys, manifested as changes in haematological parameters, splenomegaly, and moderate to heavy haemosiderosis in spleen, liver, and kidney, partially accompanied by extramedullary haematopoiesis. These effects occur secondary to excessive compound-induced haemolysis and are consistent with a regenerative anaemia. The LOAELs (lowest tested dosages; NOELs not derivable) for significant increases in methaemoglobin levels have been reported for a 13-week oral (gavage) exposure as 5 mg/kg body weight in rats and 7.5 mg/kg body weight in mice and 2 mg/kg body weight per day for 26–103 weeks’ oral (gavage) application to rats. Fibrotic changes of the spleen were observed in male rats, with a LOAEL of 2 mg/kg body weight per day, and hyperplasia of bone marrow was seen in female rats, with a LOAEL of 6 mg/kg body weight per day (103-week gavage) (Table 5; NTP, 1989; Chhabra et al., 1991).

There seem to be species differences not only in rates of metabolic clearance, but also in the levels of crucial enzymes (e.g., NADH-dependent methaemoglobin reductase located in the erythrocytes). Enzymatic activity in rat and mouse erythrocytes is 5 and 10 times higher, respectively, than that in human erythrocytes, suggesting that humans are more susceptible to this toxic effect. This is also reported for aniline, where the oral dose for acute methaemoglobinaemia seems to be 10–100 times less than that for rats or dogs, calculated on a body weight basis (EU, 2002). However, available data are inadequate to quantify these species differences for PCA.

Regarding intraspecies differences, in the study on haemoglobin adducts in workers occupationally exposed to PCA, it could be shown that workers who were slow acetylators showed a significantly increased haemoglobin adduct level compared with fast acetylators. (About 50% of the European population, for example, are slow acetylators as a result of a genetically caused lower activity of N-acetyltransferase, with increased sensitivity to compounds such as PCA.)

The scarce data on the effects on humans of occupational exposure to PCA are mostly from a few older reports of severe intoxications after accidental exposure during production, with symptoms of cyanosis and methaemoglobinaemia. No dose–effect correlations can be derived because of the absence of characterizations of the exposure or the body burden. Haemoglobin adducts were observed after PCA exposure and have been used in the biomonitoring of workers employed in the synthesis and processing of PCA.

There are reports of premature neonates being inadvertently exposed to PCA as a breakdown product of chlorohexidine. Three neonates in one report (14.5–43.5% methaemoglobin) and 33 of 415 neonates in another report (6.5–45.5% methaemoglobin, mean 19%, during the 8-month screening period) were found to be methaemoglobin positive. A prospective clinical study showed that immaturity, severe illness, time exposed to PCA, and low concentrations of NADH reductase probably contributed to the condition. Fetal haemoglobin is more easily oxidized than adult haemoglobin; further, the delicate skin of the premature neonate is more permeable (see section 9).

PCA is carcinogenic in male rats, with the induction of unusual and rare tumours of the spleen (fibrosarcomas and osteosarcomas), which is typical for aniline (EU, 2002) and related substances. In the NTP (1989) study, PCA was found to be carcinogenic in male rats, based on the increased incidence of splenic sarcoma, osteosarcoma, and haemangiosarcoma in high-dose (18 mg/kg body weight) rats. The dose–response was non-linear, the incidence of sarcomas at 2 and 6 mg/kg body weight being marginal.

In female rats, the precancerous stages of the spleen tumours are increased in frequency. Increased incidences of pheochromocytoma of the adrenal gland in male and female rats may have been related to PCA administration.

PCA induced hepatocellular tumours in male mice and a marginal to significant increase in the incidences of haemangiosarcoma in male and female mice (Table 9; NTP, 1989; Chhabra et al., 1991).

Whether the mechanism of carcinogenesis is mediated through genotoxic or non-genotoxic events is unresolved. PCA is genotoxic in vitro but appears to be dependent on metabolism for its full expression.

There were no data available concerning carcinogenicity in humans associated with PCA exposure.

11.1.2 Criteria for setting tolerable intakes/tolerable concentrations for 4-chloroaniline

As available data indicate that PCA is a carcinogen, exposure should be reduced to the extent possible.

A tolerable intake for non-neoplastic effects is based on the significant increases in methaemoglobin levels in rats and mice and fibrotic changes of the spleen in male rats.

The LOAELs (lowest tested dosages, NOELs not derivable) for significant increases of methaemoglobin have been reported for a 13-week oral exposure by gavage of 5 mg/kg body weight in rats and 7.5 mg/kg body weight in mice and 2 mg/kg body weight per day for 26–103 weeks’ oral (gavage) application to rats.

In male rats, fibrotic changes of the spleen were described at the lowest dose tested (LOAEL of 2 mg/kg body weight per day). This is the same dose as the LOAEL in rats for significant increases in methaemoglobin level. A NOEL was not available.

If one applied the uncertainty factors 10 (for use of a LOAEL rather than a NOEL) × 10 (for interspecies extrapolation) × 10 (for interindividual variability) to the LOAEL of 2 mg/kg body weight per day, one could derive a tolerable intake (IPCS, 1994) of 2 µg/kg body weight per day.

In premature babies (mean birth weight about 1.2 kg), an exposure to 0.3 mg/day (equivalent to 0.25 mg/kg body weight per day) (dermal/inhalation) caused a mean methaemoglobin concentration of 19% (6.5–45.5%). Therefore, the NOAEL must have been much lower. Further, the exposure was comparatively short, there being 1–18 methaemoglobin-positive days (mean 6 days). It is clear that premature babies are much more susceptible than healthy workers. First, the reducing capacity of NADH reductase in neonates is downgraded and not fully developed. Further, fetal haemoglobin is more easily oxidized than the adult form, and the delicate skin of the premature neonate is more permeable.

11.1.3 Sample risk characterization

Workers may be exposed to PCA via inhalation and skin contact during the production and processing of PCA and in the printing and dyeing industries where PCA-based azo dyes and pigments are used.

Recent data on PCA concentrations at the workplace during production are not available for a risk characterization. It is to be hoped that the cited older figures of 58 and 63 mg/m³ (which resulted in toxic effects) and even of 0.2–2.0 mg/m³ are no longer found in any countries producing and processing PCA.

From studies at dyeing factories, especially during weighing/mixing operations, a workshift inhalation intake of PCA of <4 ng/kg body weight per day can be calculated (see section 6.2.1).

There is a large potential for consumer exposure to PCA from the use of dyed/printed textiles and papers and cosmetic and pharmaceutical products. The exposure can result from residual PCA in the commercial product and/or from hydrolytic or metabolic degradation of the product during use. It can be dermal (wearing of clothes, use of deodorant products or mouthwashes) or oral (small children sucking clothes and other materials, use of mouthwashes).

Sample estimates of maximal consumer exposure (details given in section 6.2.2) are as given in Table 11.

Table 11: Sample estimates of maximal consumer exposure.

In addition, for young children, an oral exposure from the sucking of dyed textiles may occur, which could be in the range of several micrograms per kilogram body weight per day. Although each estimate in itself is not certain enough to be used for a quantitative risk characterization for each individual route of exposure, it can be seen that consumers are exposed via a number of possible routes, leading in total to exposure concentrations of about 0.1–0.3 µg/kg body weight per day, assuming only 1% penetration by clothes.

Considering only non-neoplastic effects (i.e., methaemoglobinaemia), these possible human exposures are within an order of magnitude of the calculated tolerable intake of 2 µg/kg body weight per day (see section 11.1.2). Incidental exposure to high concentrations of PCA can be fatal.

Further effects of concern are carcinogenicity and possibly skin sensitization.

11.1.4 Uncertainties in the evaluation of human health effects

There are no reliable data on occupational exposure levels PCA or on exposure of the general population to PCA.

Therefore, it was not possible to make a risk estimate for PCA production workers. Methaemoglobinaemia in premature babies as a result of PCA exposure is reported, but it is recognized that neonates are much more susceptible than healthy workers, and it is therefore difficult to make an evaluation using these data.

Data were not available to determine a NOAEL instead of a LOAEL for methaemoglobin formation and fibrotic changes of the spleen.

The effect of PCA on the reproductive system cannot be evaluated due to lack of data.

11.2.1 Evaluation of effects in surface waters

The main environmental target compartment of PCA from its industrial use as an intermediate in the production of pesticides, azo dyes and pigments, and cosmetic products is the hydrosphere.

In surface waters, PCA is rapidly degraded by direct photolysis (half-life 2–7 h), whereas biodegradation is expected to be of minor importance. Elimination observed in experiments with different microbial inocula could be largely attributed to abiotic processes (e.g., photodegradation or adsorption). Thus, under conditions not favouring biotic or abiotic removal, adsorption of PCA to sediment particles in surface waters can be expected, as can application of PCA to agricultural soils in sewage sludges.

The available experimental bioconcentration data, as well as the measured n-octanol/water partition coefficients, indicate no bioaccumulation potential for PCA in aquatic organisms.

A sample risk characterization with respect to the aquatic environment may be performed by calculating the ratio between a (local or regional) predicted environmental concentration (PEC; based on measured or model concentrations) and a predicted no-effect concentration (PNEC) (EC, 1996).

A quantification of PCA releases from all the different industrial sources is not possible with the available data. As a first approach, however, the measured concentrations in the river Rhine and its tributaries can be taken as a basis for a sample risk characterization, as this area is one of the most heavily industrialized areas in the EU. There, the concentration range is between about 0.1 and 1 µg/litre. The higher concentration was taken as the PEC.

A PNEC for surface waters may be calculated by dividing the lowest valid NOEC by an appropriate uncertainty factor:

PNEC	= (10 µg/litre) / 10
	= 1 µg/litre

where:

10 µg/litre is the lowest NOEC value from a long-term study with Daphnia magna. The lower EC₁₀ value of 3 µg/litre found for fluorescence inhibition after a light pulse in the alga Scenedesmus subspicatus is not regarded as relevant and appropriate for risk characterization purposes.

10 is chosen as the uncertainty factor. According to EC (1996), this factor should be applied when long-term toxicity NOECs are available from at least three species across three trophic levels (e.g., fish, daphnia, algae).

Therefore, based upon the highest measured PCA concentrations in the river Rhine and its tributaries, the PEC/PNEC ratio is 1. In EU jurisdiction, for substances exhibiting ratios of less than or equal to 1, further information and/or testing as well as risk reduction measures beyond those that are already being applied are not required.

Figure 3: Plot of reported toxicity values for PCA in aquatic organisms.

The range of values for the adverse effects of PCA on aquatic species of different trophic levels, experimentally determined in short- and long-term tests, is given in Figure 3.

PCA released to surface water that contains low amounts of organic matter is expected to undergo rapid photodegradation. In waters with significant amounts of particulate matter, however, photooxidation may be reduced, and adsorption to organic material may increase. Therefore, a possible risk for aquatic organisms, particularly benthic species, cannot be completely ruled out. The only benthic species tested (Chironomus plumosus larvae) exhibited no significant sensitivity (48-h EC₅₀ of 43 mg/litre for immobilization). However, the test medium used was reconstituted water and contained no elevated levels of organic matter. Moreover, experiments with Daphnia magna revealed significantly reduced toxicity with increasing concentrations of dissolved humic materials in the medium, possibly caused by reduced bioavailability of PCA from adsorption to dissolved humic materials. Furthermore, bioaccumulation in aquatic species was reported to be very low. Therefore, from the available data, a significant risk associated with exposure of aquatic organisms to PCA is not to be expected.

11.2.2 Evaluation of effects on terrestrial species

The use of phenylurea herbicides or insecticides may lead to the contamination of agricultural soils with PCA. A measurement programme on agricultural soils in Bavaria, Germany, gave about 15% positive samples. The concentration range in the positive samples was between 5 and 50 µg/kg (BUA, 1995). It cannot be judged whether these data are representative for other regions of the world. However, due to the lack of other data, they are used for the risk characterization.

The measured data on PCA concentrations in biota due to the use of pesticides are somewhat conflicting. In wild (mushrooms, berries) and cultured plants (spinach, cress, potatoes), PCA was not detected after insecticide application, whereas it was found in tissue samples of fish in concentrations of about 1 mg/kg. As this is a single finding, a proper sample risk characterization is not possible due to the high degree of uncertainty.

Soil sorption coefficients determined in a variety of soil types indicate only a low potential for soil sorption. In most experiments, soil sorption increased with increasing organic matter and decreasing pH values. As a consequence, under conditions unfavourable for abiotic and biotic degradation, leaching of PCA from soil into groundwater, particularly in soils with a low organic matter content and elevated pH levels, may occur.

For the terrestrial compartment, toxicity tests on microbial activity, higher plants, and earthworms are available. None of the studies seems appropriate to serve as a basis for a quantitative risk characterization. The lowest effect value reported for turnip (Brassica rapa) was 66.5 mg/kg and exceeds the soil concentrations measured in agricultural soils (Bavaria, Germany; cited above) by a factor of approximately 1000. Therefore, PCA is not expected to pose a significant risk for the tested terrestrial species. Valid studies on the toxicity of PCA to terrestrial vertebrates or on effects of PCA on ecosystems are not available.

11.2.3 Uncertainties in the evaluation of environmental effects

Regarding the effects of PCA on aquatic species, the toxicity data set includes a variety of species from different trophic levels. Most studies are of good quality and acceptable for risk characterization purposes. Only one test is available for benthic species that may be exposed to PCA adsorbed to organic matter. However, this test has been performed in reconstituted water without elevated levels of particulate matter. For the terrestrial compartment, the available toxicity studies cannot be regarded as adequate for a quantitative risk characterization.

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For the BUA review process, the company that is in charge of writing the report (usually the largest producer in Germany) prepares a draft report using literature from an extensive literature search as well as internal company studies.

In this BUA report, the toxicological sections were prepared by Berufsgenossenschaft der Chemischen Industrie (BG Chemie, Toxicological Evaluation No. 9). The draft document is subject to a peer review in several readings of a working group consisting of representatives from government agencies, the scientific community, and industry.

The authors of this BUA report were Drs A. Boehncke, J. Kielhorn, G. Könnecker, C. Pohlenz-Michel, and I. Mangelsdorf of the Fraunhofer Institute of Toxicology and Aerosol Research, Drug Research and Clinical Inhalation, Hanover, Germany.

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The scientific documents of the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) are based on critical evaluations of the available toxicological and occupational medical data from extensive literature searches and of well documented industrial data. The evaluation documents involve a critical examination of the quality of the database, indicating inadequacy or doubtful validity of data and identification of data gaps. This critical evaluation and the classification of substances are the result of an extensive discussion process by the members of the Commission proceeding from a draft document prepared by members of the Commission, by ad hoc experts, or by the Scientific Secretariat of the Commission. Scientific expertise is guaranteed by the members of the Commission, consisting of experts from the scientific community, industry, and employers’ associations.

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The members of the Peer Review Panel who evaluated the draft Technical Report on p-chloroaniline hydrochloride on 8 April 1988 are listed below. Panel members serve as independent scientists, not as representatives of any institution, company, or governmental agency. In this capacity, Panel members have five major responsibilities: (a) to ascertain that all relevant literature data have been adequately cited and interpreted, (b) to determine if the design and conditions of the NTP studies were appropriate, (c) to ensure that the Technical Report presents the experimental results and conclusions fully and clearly, (d) to judge the significance of the experimental results by scientific criteria, and (e) to assess the evaluation of the evidence of carcinogenicity and other observed toxic responses.

National Toxicology Program Board of Scientific Counselors

Technical Reports Review Subcommittee

Robert A. Scala (Chair), Exxon Corporation, East Millstone, NJ

Michael A. Gallo (Principal Reviewer), Department of Environmental and Community Medicine, Rutgers Medical School, Piscataway, NJ

Frederica Perera, School of Public Health, Columbia University, New York, NY (unable to attend)

Ad Hoc Subcommittee Panel of Experts

John Ashby, Imperial Chemical Industries, PLC, Alderley Park, England

Charles C. Capen, Department of Veterinary Pathobiology, Ohio State University, Columbus, OH

Vernon M. Chinchilli, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA

Kim Hooper, Department of Health Services, State of California, Berkeley, CA

Donald H. Hughes (Principal Reviewer), Regulatory Services Division, The Procter and Gamble Company, Cincinnati, OH

William Lijinsky, Frederick Cancer Research Facility, Frederick, MD

Franklin E. Mirer, United Auto Workers, Detroit, MI (unable to attend)

James A. Popp, Chemical Industry Institute of Toxicology, Research Triangle Park, NC

Andrew Sivak (Principal Reviewer), Arthur D. Little, Inc., Cambridge, MA

The draft CICAD on 4-chloroaniline was sent for review to institutions and organizations identified by IPCS after contact with IPCS national Contact Points and Participating Institutions, as well as to identified experts. Comments were received from:

M. Baril, International Programme on Chemical Safety/Institut de Recherches en Santé et en Sécurité du Travail du Québec, Montreal, Quebec, Canada

R. Benson, Drinking Water Program, US Environmental Protection Agency, Denver, CO, USA

R Cary, Health and Safety Executive, Bootle, Merseyside, United Kingdom

R. Chhabra, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA

S. Dobson, Centre for Ecology and Hydrology, Monks Wood, United Kingdom

H. Galal-Gorchev, US Environmental Protection Agency, Washington DC, USA

H. Gibb, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA

R.F. Hertel, Federal Institute for Health Protection of Consumers and Veterinary Medicine, Berlin, Germany

C. Hiremath, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA

S. Humphreys, Food and Drug Administration, Washington, DC, USA

H. Nagy, National Institute for Occupational Safety and Health, Cincinnati, OH, USA

H.G. Neumann, Würzberg University, Würzberg, Germany

D. Singh, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA

E. Soderlund, National Institute of Public Health, Oslo, Norway

K. Ziegler-Skylakakis, GSF-Forschungszentrum für Umvelt und Gesundheit, Neuherberg, Oberschleissheim, Germany

Ottawa, Canada,

29 October – 1 November 2001

Members

Mr R. Cary, Health and Safety Executive, Merseyside, United Kingdom

Dr T. Chakrabarti, National Environmental Engineering Research Institute, Nehru Marg, India

Dr B.-H. Chen, School of Public Health, Fudan University (formerly Shanghai Medical University), Shanghai, China

Dr R. Chhabra, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA (teleconference participant)

Dr C. De Rosa, Agency for Toxic Substances and Disease Registry, Department of Health and Human Services, Atlanta, GA, USA (Chairman)

Dr S. Dobson, Centre for Ecology and Hydrology, Huntingdon, Cambridgeshire, United Kingdom (Vice-Chairman)

Dr O. Faroon, Agency for Toxic Substances and Disease Registry, Department of Health and Human Services, Atlanta, GA, USA

Dr H. Gibb, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA

Ms R. Gomes, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada

Dr M. Gulumian, National Centre for Occupational Health, Johannesburg, South Africa

Dr R.F. Hertel, Federal Institute for Health Protection of Consumers and Veterinary Medicine, Berlin, Germany

Dr A. Hirose, National Institute of Health Sciences, Tokyo, Japan

Mr P. Howe, Centre for Ecology and Hydrology, Huntingdon, Cambridgeshire, United Kingdom (Co-Rapporteur)

Dr J. Kielhorn, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany (Co-Rapporteur)

Dr S.-H. Lee, College of Medicine, The Catholic University of Korea, Seoul, Korea

Ms B. Meek, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada

Dr J.A. Menezes Filho, Faculty of Pharmacy, Federal University of Bahia, Salvador, Bahia, Brazil

Dr R. Rolecki, Nofer Institute of Occupational Medicine, Lodz, Poland

Dr J. Sekizawa, Division of Chem-Bio Informatics, National Institute of Health Sciences, Tokyo, Japan

Dr S.A. Soliman, Faculty of Agriculture, Alexandria University, Alexandria, Egypt

Dr M.H. Sweeney, Document Development Branch, Education and Information Division, National Institute for Occupational Safety and Health, Cincinnati, OH, USA

Dr J. Temmink, Department of Agrotechnology & Food Sciences, Wageningen University, Wageningen, The Netherlands

Ms D. Willcocks, National Industrial Chemicals Notification and Assessment Scheme (NICNAS), Sydney, Australia

Representative of the European Union

Dr K. Ziegler-Skylakakis, European Commission, DG Employment and Social Affairs, Luxembourg

Observers

Dr R.M. David, Eastman Kodak Company, Rochester, NY, USA

Dr R.J. Golden, ToxLogic LC, Potomac, MD, USA

Mr J.W. Gorsuch, Eastman Kodak Company, Rochester, NY, USA

Mr W. Gulledge, American Chemistry Council, Arlington, VA, USA

Mr S.B. Hamilton, General Electric Company, Fairfield, CN, USA

Dr J.B. Silkworth, GE Corporate Research and Development, Schenectady, NY, USA

Dr W.M. Snellings, Union Carbide Corporation, Danbury, CN, USA

Dr E. Watson, American Chemistry Council, Arlington, VA, USA

Secretariat

Dr A. Aitio, International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland

Mr T. Ehara, International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland

Dr P. Jenkins, International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland

CHLOROANILINE ICSC:0026

Le présent CICAD consacré à la 4-chloroaniline (p-chloroaniline ) a été préparé par l'Institut Fraunhofer de toxicologie et de recherche sur les aérosols , de Hanovre (Allemagne). Il s'inspire de rapports établis par le Comité consultatif de la Société allemande de chimie sur les substances chimiques d'importance écologique (BUA, 1993a) , par la Commission allemande MAK (MAK,1992), par l'Union allemande des industries chimiques (BG Chemie,1994 ) et par le Programme toxicologique national des Etats-Unis (NTP, 1989). En mars 2001,il a été procédé à un dépouillement bibliographique exhaustif des bases de données correspondantes , afin de rechercher toute référence intéressante à des publications postérieures aux rapports en question. Des informations sur la préparation et l'examen par des pairs des sources documentaires utilisées sont données à l'appendice 1. L'appendice 2 fournit des renseignements sur l'examen par des pairs du présent CICAD. Ce CICAD a été approuvé en tant qu'évaluation internationale lors d'une réunion du Comité d'évaluation finale qui s'est tenue à Ottawa (Canada) du 29 octobre au 1er novembre 2001. La liste des participants à cette réunion figure à l'appendice 3. La fiche internationale sur la sécurité chimique de la 4-chloroaniline (ICSC 0026) , établie par le Programme international sur la sécurité chimique (IPCS, 2002) , est également reproduite dans le présent document.

Les anilines chlorées en position 2-, 3-, et 4- (ortho-, méta- et para- ) ont sensiblement les mêmes utilisations. Ces trois isomères sont tous hémotoxiques et leurs propriétés toxiques sont identiques chez le rat et la souris, la 4-chloroaniline étant dans tous les cas celui des trois qui produit les effets les plus graves. La 4-chloroaniline se révèle génotoxique dans divers systèmes d'épreuve (voir plus loin) , alors que la 2- et la 3-chloroaniline donnent à cet égard des résultats irréguliers, qui correspondent à une génotoxicité faible ou nulle. C'est pourquoi le présent CICAD ne concerne que la 4-chloroaniline, c'est-à-dire à la plus toxique des chloranilines.

La 4-chloroaniline ou parachloroaniline (désignée dans la suite du texte par le sigle PCA) (No CAS 106-47-8 ), se présente sous la forme d'un solide cristallin incolore à légèrement ambré dégageant une faible odeur aromatique. Elle est soluble dans l'eau et dans les solvants organiques courants. Sa tension de vapeur et son coefficient de partage entre le n-octanol et l'eau sont modérément élevés. Elle se décompose en présence d'air et de lumière ainsi qu'à température élevée.

On utilise la PCA comme intermédiaire dans la fabrication d'un certain nombre de produits, notamment des produits agrochimiques, des colorants et des pigments azoïques, des cosmétiques et des produits pharmaceutiques. Les rejets de PCA dans l'atmosphère peuvent donc provenir de sources industrielles diverses (production, transformation, teinture, impression ).

Compte tenu des utilisations de la PCA, on peut s'attendre à ce que l'hydrosphère soit le principal compartiment de l'environnement où se retrouve ce composé. Dans le Rhin et ses affluents par exemple, on en trouve à une concentration qui se situe à peu près entre 0,1 et 1 μg/litre. Dans l'hydrosphère, la PCA se décompose rapidement sous l'action de la lumière (demi-vie mesurée : 2 à 7 h). Le calcul de la demi-vie du composé dans l'air en prenant en compte sa réaction avec les radicaux hydroxyle donne une valeur de 3,9 h . Les nombreuses études consacrées à la biodégradation de la PCA indiquent que ce composé est intrinsèquement biodégradable dans l'eau en aérobiose, aucune minéralisation importante n'étant par contre décelée en anaérobiose.

Les coefficients de sorption dans divers types de sols déterminés d'après l'isotherme de sorption de Freundlich indiquent que les possibilités sont limitées à cet égard. Dans la plupart des expériences, on a constaté que la sorption aux particules du sol était d'autant plus importante que la teneur en matières organiques était élevée et le pH faible. Il en résulte que lorsque les conditions ne favorisent pas une décomposition biotique ou abiotique, la PCA peut passer du sol dans les eaux souterraines par lessivage, lorsque le sol est pauvre en matières organiques et que son pH est élevé. Les données expérimentales dont on dispose au sujet de la bioconcentration du composé ainsi que les valeurs mesurées de son coefficient de partage entre le n-octanol et l'eau, indiquent que la PCA n'a pas tendance à s'accumuler dans les organismes aquatiques.

La PCA est rapidement résorbée et métabolisée. Les principales voies métaboliques de ce composé sont les suivantes : a) une C-hydroxylation en position ortho conduisant au 2-amino-5-chlorophénol, suivie d'une sulfoconjugaison en sulfate de 2-amino-5-chlorophényle, lequel est excrété tel quel ou après N-acétylation en sulfate de N-acétyl-2-amino-5-chlorophényle ; b) une N-acétylation en 4-chloroacétanilide (que l'on retrouve principalement dans le sang ) , qui est transformé à son tour en 4-chloroglycolanilide, puis en acide 4-chlorooxanilique (que l'on retrouve dans l'urine ) ; c) une N-oxydation en 4-chlorophénylhydroxylamine puis en 4-chloronitrosobenzène (présent dans les érythrocytes).

Les métabolites réactifs de la PCA forment des liaisons covalentes avec l'hémoglobine et les protéines du foie et du rein. Chez l'Homme , on peut peut déjà mettre en évidence des adduits à l'hémoglobine 30 minutes après une exposition accidentelle , leur concentration étant maximale au bout de 3 h. Les sujets qui sont des acétylateurs lents ont davantage tendance à former des adduits à l'hémoglobine que les acétylateurs rapides.

Chez l'Homme et l'animal , l'excrétion est essentiellement urinaire , la PCA et ses conjugués apparaissant déjà 30 minutes après l'exposition. L'excrétion se produit au cours des 24 premières heures et elle est presque complète au bout de 72 h.

En ce qui concerne la DL₅₀ par voie orale , on indique des valeurs de 300 à 420 mg/kg de poids corporel pour le rat, de 228 à 500 mg/kg p.c. pour la souris et de 350 mg/kg p.c. pour le cobaye. Des valeurs du même ordre ont été obtenues pour la voie intrapéritonéale et cutanée chez le rat, le lapin et le chat. On a trouvé une CL₅₀ de 2340mg/m³ chez le rat. L'effet toxique principal consiste dans la formation de méthémoglobine. A cet égard, la PCA est plus active et plus rapide que l'aniline. La PCA est également capable de produire des effets néphrotoxiques et hépatotoxiques.

Chez le lapin, la PCA ne provoque pas d'irritation cutanée , mais seulement une légère irritation de la muqueuse oculaire. On a mis en évidence un faible pouvoir sensibilisateur dans plusieurs systèmes d'épreuve.

Une exposition répétée à la PCA entraîne une cyanose et une méthémoglobinémie, suivies d'effets sanguins, hépatiques, spléniques et rénaux qui se manifestent par des anomalies hématologiques, une splénomégalie ainsi que par une hémosidérose modérée à forte au niveau de la rate, du foie et du rein, partiellement accompagnée d'une hémopoïèse extramédullaire. Ces effets sont consécutifs à une hémolyse excessive provoquée par ce composé et correspondent à une anémie régénérative. La valeur de la dose la plus faible provoquant un effet nocif observable (LOAEL ; il n'est pas possible d'obtenir une valeur pour la NOEL ou dose sans effet observable) , à savoir une augmentation sensible de la méthémoglobinémie chez le rat et la souris, est respectivement égale à 5 et 7,5 mg/kg p.c. par jour pour une durée d'administration de 13 semaines par gavage (à raison de 5 jours par semaines). Elle a été trouvée égale à 2 mg/kg p.c. par jour pour des rats qui avaient reçu de la PCA , également par gavage, à raison de 5 jours par semaine pendant des durées de 26 , 52 , 78 et 103 semaines. On a observé une fibrose de la rate chez les rats mâles pour une LOAEL de 2 mg/kg p.c.par jour et une hyperplasie de la moelle osseuse chez les femelles pour une LOAEL de 6 mg/kg p.c. par jour (administration par gavage sur une période de 103 semaines).

La PCA est cancérogène pour le rat mâle, chez lequel elle provoque la formation de tumeurs spléniques inhabituelles et rares (fibrosarcomes et ostéosarcomes) qui sont caractéristiques de l'aniline et des substances apparentées. Chez la ratte, on constate une augmentation de la fréquence des stades précancéreux des tumeurs spléniques. On pense également que l'augmentation de l'incidence des phéochromocytomes de la surrénale pourrait être due à l'administration de PCA. On a également relevé des signes de cancérogénicité chez la souris mâle , se traduisant par des tumeurs hépatocellulaires et des hémangiosarcomes.

Les tests de transformation cellulaire effectués sur PCA se révèlent positifs. Selon diverses épreuves de génotoxicité in vitro (test de mutagénicité sur salmonelles, test du lymphome de souris, test des aberrations chromosomiques , induction d'échanges entre chromatides soeurs ) , la PCA pourrait être génotoxique , mais les résultats obtenus sont parfois contradictoires. En raison du manque de données, il est impossible de se prononcer sur la génotoxicité in vivo de la PCA.

On ne dispose d'aucune étude relative à la toxicité de la PCA pour la fonction reproductrice (toxicité génésique).

Les données concernant l'exposition professionnelle humaine à la PCA sont pour l'essentiel tirées de quelques rapports médicaux anciens portant sur des cas graves d'intoxication consécutifs à une exposition accidentelle au composé pendant la production. Les symptômes observés sont notamment les suivants : augmentation de la méthémoglobinémie et de la sulfhémoglobinémie , cyanose, apparition d'une anémie et d'anomalies d'origine anoxique. La PCA a fortement tendance à former des adduits avec l'hémoglobine dont la recherche et le dosage peuvent être utiles pour la surveillance biologique des travailleurs exposés à la 4-chloraniline sur le lieu de travail.

On a fait état dans deux pays de cas de méthémoglobinémie grave chez des nouveau-nés provenant d'unités de soins néonatals intensifs où des prématurés s'étaient trouvés exposés à de la PCA issue de la décomposition de la chlorhexidine ; la chlorhexidine, ajoutée par inadvertance au liquide utilisé pour l'humidification, s'était en effet décomposée en parachloraniline sous l'effet de la chaleur produite par un incubateur d'un type nouveau. Selon un rapport, trois nouveau-nés (14,5-43,5 % de méthémoglobine ) et 33 sur 415 selon un autre rapport (6,5-45,5 % de méthémoglobine au cours de la période de dépistage de 8 mois ) se sont révélés porteurs de méthémoglobine. Une étude clinique prospective a montré que l'immaturité, une maladie grave , la durée d'exposition à la PCA et une faible concentration en NADH ont probablement contribué à cette pathologie.

Selon les résultats considérés comme valables des tests de toxicité effectués sur divers organismes aquatiques, on peut classer la PCA comme modérément à fortement toxique pour les biotes du compartiment aquatique. La concentration la plus faible sans effet observable (NOEC) qui ressort des études de longue durée sur des organismes dulçaquicoles (Daphnia magna, NOEC à 21 jours 0,01 mg/litre ) est dix fois plus forte que les valeurs maximales mesurées dans le Rhin et ses affluents au cours des années 1980 et 1990. On ne peut donc totalement exclure un risque pour les organismes aquatiques , notamment les espèces benthiques , en particulier dans les eaux où la présence d'une quantité importante de matières particulaires empêche une photominéralisation rapide. Toutefois la seule espèce benthique qui ait été étudié à cet égard ne présente pas de sensibilité particulière au composé (CE₅₀ à 48 h , 43 mg/litre) et l'expérimentation sur la daphnie montre que la toxicité est sensiblement réduite lorsque la concentration en matières humiques dissoutes augmente dans le milieu, peut-être du fait que l'adsorption de la PCA sur ces matières en réduit la biodisponibilité. De plus, la bioaccumulation du composé par les espèces aquatiques semble très faible. Dans ces conditions, on peut conclure sur la base des données disponibles que la PCA ne représente pas un risque important pour les organismes aquatiques.

Selon les données relatives aux microorganismes et aux végétaux, la PCA n'est que modérément toxique pour le milieu terrestre. Il est existe une marge de sécurité correspondant à un facteur 1000 entre les effets toxiques signalés et les concentrations relevées dans le sol.

L'évaluation de l'exposition des consommateurs à la PCA par les diverses voies envisageables conduit à une exposition totale journalière ne dépassant pas 300 ng/kg de poids corporel, en supposant que la pénétration par les vêtements n'est que de 1 %. En ne prenant en compte que les effets non néoplasiques (c'est-à-dire la méthémoglobinémie), cette exposition humaine possible est inférieure d'un ordre de grandeur à la dose journalière tolérable calculée qui est égale à 2 μg /kg de poids corporel. Une exposition aiguë à une forte concentration de PCA peut être mortelle.

Les autres effets que l'on peut redouter sont la cancérogénicité et le pouvoir de sensibilisation cutanée de ce composé.

Les résidus de PCA qui subsistent dans les produits de consommation doivent encore être réduits, voire totalement éliminés.

El presente CICAD sobre la 4-cloroanilina (p-cloroanilina) fue preparado por el Instituto Fraunhofer de Toxicología y de Investigación sobre los Aerosoles, de Hannover (Alemania). Se basa en informes compilados por el Comité Consultivo Alemán sobre las Sustancias Químicas Importantes para el Medio Ambiente (BUA, 1993a), la Comisión Alemana MAK (MAK, 1992), la Unión Alemana de la Industria Química (BG Chemie, 1994) y el Programa Nacional de Toxicología de los Estados Unidos (NTP, 1989). En marzo de 2001 se realizó una búsqueda bibliográfica amplia de bases de datos pertinentes para localizar cualquier referencia de interés publicada después de las incorporadas a estos informes. La información relativa a la preparación y el examen colegiado de los documentos originales figura en el Apéndice 1. La información sobre el examen colegiado de este CICAD se presenta en el Apéndice 2. Este CICAD se aprobó en una reunión de la Junta de Evaluación Final celebrada en Ottawa (Canadá) del 29 de octubre al 1º de noviembre de 2001. La lista de participantes en la Junta de Evaluación Final figura en el Apéndice 3. También se reproduce en este documento la Ficha internacional de seguridad química (ICSC 0026) para la 4-cloroanilina, preparada por el Programa Internacional de Seguridad de las Sustancias Químicas (IPCS, 2002).

Las anilinas cloradas en las posiciones 2-, 3- y 4- (orto-, meta- y para-) tienen los mismos tipos de aplicaciones. Todos los isómeros de la cloroanilina son hematotóxicos y muestran la misma pauta de toxicidad en ratas y ratones, pero en todos los casos cabe atribuir a la 4-cloroanilina los efectos más graves. La 4-cloroanilina es genotóxica en diversos sistemas (véase infra), mientras que los resultados para la 2- y la 3-cloroanilina no son uniformes e indican efectos genotóxicos débiles o nulos. Por consiguiente, este CICAD se concentra sólo en la 4-cloroanilina como la sustancia más tóxica de las anilinas cloradas.

La 4-cloroanilina (denominada en lo sucesivo PCA) (CAS Nº 106-47-8) es una sustancia sólida cristalina entre incolora y ligeramente ámbar, con un suave olor aromático. Es soluble en agua y en los disolventes orgánicos normales. Tiene una presión de vapor y un coeficiente de reparto n-octanol/agua moderados. Se descompone en presencia de la luz y el aire y a temperaturas elevadas.

La PCA se utiliza como intermediario en la fabricación de diversos productos, entre ellos sustancias químicas para la agricultura, colorantes y pigmentos azoicos, cosméticos y productos farmacéuticos. Así pues, se pueden producir emisiones de PCA a la atmósfera a partir de varias fuentes industriales (por ejemplo, la industria de producción, elaboración, teñido/impresión).

A partir de los tipos de aplicaciones se puede predecir que el principal compartimento destinatario de la sustancia química en el medio ambiente es la hidrosfera. Las concentraciones medidas, por ejemplo, en el Rin y sus afluentes son de alrededor de 0,1 y 1 µg/l. En la hidrosfera, la PCA se degrada con rapidez bajo la influencia de la luz (semividas medidas de 2 a 7 h). Se ha calculado una semivida de la sustancia química en el aire para la reacción con los radicales hidroxilo de 3,9 h. Numerosos estudios sobre la biodegradación de la PCA indican que se trata de una sustancia fundamentalmente biodegradable en el agua en condiciones aerobias, mientras que no se ha detectado una mineralización significativa en condiciones anaerobias.

Los coeficientes de sorción en diversos tipos de suelos, determinados de acuerdo con la isoterma de sorción de Freundlich, indican sólo un bajo potencial de sorción en el suelo. En numerosos experimentos, la sorción en el suelo aumentó con el incremento de la materia orgánica y la disminución de los valores del pH. Por consiguiente, en condiciones desfavorables para la degradación abiótica y biótica se puede producir lixiviación de la PCA desde el suelo hacia el agua freática, particularmente en suelos con un bajo contenido de materia orgánica y niveles elevados de pH. Los datos experimentales disponibles sobre bioconcentración, así como los coeficientes de reparto n-octanol/agua medidos, indican que la PCA no tiene potencial de bioacumulación en los organismos acuáticos.

La PCA se absorbe y metaboliza con rapidez. Sus principales vías metabólicas son las siguientes: a) C-hidroxilación en la posición orto para formar 2-amino-5-clorofenol, seguida de una conjugación con sulfato para producir sulfato de 2-amino-5-clorofenilo, que se excreta per se o tras una N-acetilación para dar sulfato de N-acetil- 2-amino-5-clorofenilo; b) N-acetilación para formar 4-cloroacetanilida (detectada principalmente en la sangre), que a continuación se transforma en 4-cloroglicolanilida y luego en ácido 4-clorooxanílico (encontrado en la orina); o c) N-oxidación para formar 4-clorofenilhidroxilamina y luego 4-cloronitrosobenceno (en los eritrocitos).

Los metabolitos reactivos de la PCA se unen por enlace covalente a la hemoglobina y a las proteínas del hígado y el riñón. En las personas son detectables aductos de hemoglobina ya a los 30 minutos de una exposición accidental, con un nivel máximo a las tres horas. La acetilación lenta tiene un mayor potencial de formación de aductos de hemoglobina, en comparación con los acetiladores rápidos.

La excreción en los animales o las personas se produce fundamentalmente en la orina, apareciendo ya PCA y sus conjugados a los 30 minutos de la exposición. La excreción se produce fundamentalmente durante las primeras 24 horas y es casi completa a las 72 horas.

Se han notificado valores de la DL₅₀ por vía oral de 300-420 mg/kg de peso corporal para las ratas, 228-500 mg/kg de peso corporal para los ratones y 350 mg/kg de peso corporal para los cobayas. Se han obtenido valores semejantes para la administración intraperitoneal y cutánea de PCA a ratas, conejos y gatos. Se informó de un valor de la DL₅₀ para ratas de 2340 mg/m³. El efecto tóxico principal es la formación de metahemoglobina. La PCA es un inductor más potente y rápido de metahemoglobina que la anilina. También muestra un potencial nefrotóxico y hepatotóxico.

Se ha comprobado que la PCA no es un irritante de la piel en el conejo, pero sí de los ojos en grado leve. Se ha demostrado un débil potencial de sensibilización mediante varios sistemas de pruebas.

La exposición repetida a la PCA produce cianosis y metahemoglobinemia, seguidas de efectos en la sangre, el hígado, el bazo y el riñón, que se manifiestan como cambios en los parámetros hematológicos, esplenomegalia y hemosiderosis de moderada a grave en el bazo, el hígado y el riñón, parcialmente acompañada de hematopoyesis extramedular. Estos efectos se producen tras una hemólisis excesiva inducida por el compuesto y son coherentes con una anemia regenerativa. Las concentraciones más bajas con efectos adversos observados o LOAEL (no son derivables las concentraciones sin efectos observados o NOEL) para un aumento significativo de la concentración de metahemoglobina en ratas y ratones son, respectivamente, de 5 y 7,5 mg/kg de peso corporal al día con una administración de PCA mediante sonda durante 13 semanas (5 días/semana) y de 2 mg/kg de peso corporal al día para las ratas que recibieron PCA por sonda (5 días/semana) con una exposición de 26, 52, 78 y 103 semanas. Se observaron cambios fibróticos del bazo en ratas macho, con una LOAEL de 2 mg/kg de peso corporal al día, e hiperplasia de la médula ósea en ratas hembra, con una LOAEL de 6 mg/kg de peso corporal al día (por sonda durante 103 semanas).

La PCA tiene actividad carcinogénica en ratas macho, con la inducción de tumores de bazo insólitos y raros (fibrosarcomas y osteosarcomas), que son típicos de la anilina y sustancias afines. En ratas hembra aumenta la frecuencia de los estados precancerosos de los tumores de bazo. Podría haber una relación entre la mayor incidencia de feocromocitoma de la glándula adrenal en ratas macho y hembra y la administración de PCA. Se encontraron algunas pruebas de carcinogenicidad en ratas macho, en forma de tumores hepatocelulares y hemangiosarcoma.

La PCA muestra actividad en valoraciones de transformación celular. Una serie de pruebas de genotoxicidad in vitro (por ejemplo, prueba de mutagenicidad de Salmonella, valoración del linfoma del ratón, prueba de aberración cromosómica, inducción del intercambio de cromátidas hermanas) indican que la PCA es posiblemente genotóxica, aunque los resultados son a veces contradictorios. Debido a la falta de datos, no es posible sacar conclusiones acerca de la genotoxicidad de la PCA in vivo.

No se dispone de estudios sobre toxicidad reproductiva.

Los datos sobre la exposición ocupacional de las personas a la PCA proceden fundamentalmente de un pequeño número de informes más antiguos de intoxicaciones graves tras la exposición accidental a esta sustancia durante la producción. Entre los síntomas cabe mencionar niveles más elevados de metahemoglobina y sulfohemoglobina, cianosis, aparición de anemia y cambios debidos a la anoxia. La PCA tiene una fuerte tendencia a formar aductos de hemoglobina y su determinación se puede utilizar en la biovigilancia de los empleados expuestos a la 4-cloroanilina en el lugar de trabajo.

Hay informes de metahemoglobinemia en neonatos, procedentes de unidades de cuidados intensivos neonatales de dos países donde los niños prematuros estuvieron expuestos a la PCA como producto de la descomposición de clorohexidina; ésta, que se había utilizado inadvertidamente en el fluido de humidificación, se descompuso para formar PCA por la acción del calor en un nuevo tipo de incubadora. En un informe se señalaron tres casos positivos a la metahemoglobina (14,5-43,5% de metahemoglobina) y en el otro lo fueron 33 de 415 neonatos (6,5-45,5% de metahemoglobina durante el período de detección sistemática de ocho meses). En un estudio clínico prospectivo se puso de manifiesto que probablemente contribuían a ello la inmadurez, una enfermedad grave, el tiempo de exposición a la PCA y concentraciones bajas de NADH reductasa.

Basándose en los resultados de pruebas válidas disponibles sobre la toxicidad de la PCA para diversos organismos acuáticos, esta sustancia se puede clasificar como entre moderada y muy tóxica en el compartimento acuático. La concentración más baja sin efectos adversos observados (NOEC) obtenida en estudios prolongados con organismos de agua dulce (Daphnia magna, NOEC de 0,01 mg/l en 21 días) fue 10 veces superior a las concentraciones máximas determinadas en el Rin y sus afluentes durante los años ochenta y noventa. Por consiguiente, no se puede excluir por completo un posible riesgo para los organismos acuáticos, en particular las especies bentónicas, sobre todo en aguas donde hay cantidades significativas de materia particulada que inhiben la fotomineralización rápida. Sin embargo, no se observó una sensibilidad significativa en la única especie bentónica sometida a prueba (CE₅₀ de 43 mg/l a las 48 h); los experimentos con Daphnia magna pusieron de manifiesto una toxicidad muy reducida con concentraciones crecientes de materiales húmicos disueltos en el medio, posiblemente debido a la reducida biodisponibilidad de la PCA a partir de la adsorción a los materiales húmicos disueltos. Además, se informó de que la bioacumulación en las especies acuáticas era muy baja. Por consiguiente, de los datos disponibles no cabe prever un riesgo importante asociado con la exposición de los organismos acuáticos a la PCA.

Los datos disponibles sobre microorganismos y plantas indican sólo un potencial de toxicidad moderado de la PCA en el medio terrestre. Hay un margen de seguridad de 1000 veces entre los efectos notificados y las concentraciones detectadas en el suelo.

La evaluación de la exposición del consumidor a la PCA por una serie de posibles conductos da como resultado una exposición total de un máximo de 300 ng/kg de peso corporal al día, suponiendo la penetración a través de la ropa de sólo un 1%. Considerando sólo los efectos no neoplásicos (es decir, metahemoglobinemia), esta posible exposición de las personas está dentro de un orden de magnitud de la ingesta diaria tolerable calculada de 2 µg/kg de peso corporal al día. La exposición accidental aguda a concentraciones altas de PCA puede ser mortal.

Otros efectos que despiertan preocupación son la carcinogenicidad y la posible sensibilización cutánea.

Se deberían reducir o eliminar completamente las concentraciones residuales de la PCA en los productos de consumo.

ENDNOTES

    See Also:
       Toxicological Abbreviations