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International Agency for Research on Cancer (IARC) - Summaries & Evaluations

THE LEATHER TANNING AND PROCESSING INDUSTRIES

VOL.: 25 (1981) (p. 199)

5. Summary of Data Reported and Evaluation

5.1 Summary of data

There is only one case report of an adenocarcinoma of the nasal cavity occurring in a tanner. In a study in England and Wales covering the period 1961-1966, no leather tanners or processors were found among patients with adenocarcinomas or other types of nasal cancers. (See monograph on boot and shoe manufacture & repair.)

No data specifically related to laryngeal cancer in leather tanners and processors were available. In a large, multi-tumour-site case-control survey in New York state, the relative risk for developing laryngeal cancer associated with employment for more than five years in the leather industry was 5.5 (based on 6 cases).

SMRs for lung cancer in male tanners, leather dressers and curriers estimated from mortality statistics in England and Wales during the period 1921-1938 were in the order of 150. No excess was found in the study in England and Wales in 1961. SMRs for 'leather workers' in England and Wales in 1971 and for 'leather operatives' in the US were not significantly different from 100. However, in a cross-sectional study in Los Angeles in 1972-1973, the risk ratio for men engaged in 'leather-manufacturing and sales' was 1.72 (p < 0.05).

The SMR for bladder cancer in male tanners, leather dressers and curriers estimated from mortality statistics in England and Wales in the 1920s was 170. More recent reports listing SMRs for comparable occupational groups were not available to the Working Group.

An association between work in the leather trades and bladder cancer is suggested by three of four case-control studies. The one study among these that subclassified leather occupations shows that eight patients were engaged in 'preliminary' processes and tanning within the leather industry (relative risk, 1.5; not statistically significant).

No studies specifically related to lymphoma in leather tanners or processors were available. The SMR for 'leather workers' in England and Wales in 1971 was 184 for non-Hodgkin's lymphomas and 77 for Hodgkin's disease. In a large, multi-tumour-site case-control study in New York state, the relative risk for all lymphomas among 'leather workers' was 3.4 in men (based on 7 cases, p < 0.05) and 2.6 in women (based on 8 cases, p < 0.05).

In a large, multi-tumour-site case-control study in New York state, the relative risk for cancer of the oral cavity and pharynx among male 'leather workers' was 3.2 (p < 0.01, based on 18 cases). A correlation study in the US showed mortality rates for oral and pharyngeal cancer to be slightly elevated in counties with leather manufacturing industries.

Vital statistics from England and Wales and from the US suggest that death rates from renal cancer among 'leather workers' and 'employees in the leather industry' are about 1.6-2.3 times greater than those in the general population.

The SMR for cancer of the stomach in tanners in England and Wales in 1961 was 135 (p < 0.05). No data on comparable occupational groups in England and Wales at other periods or in other countries were available to the Working Group.

Inhalation of both chemical vapours and dust (including leather and hide dust) and dermal contact with these agents could occur simultaneously. For most workers, the degree and types of exposure depend upon their specific occupation and work area within the tannery. For example, the unloading of a hide-processing drum may result in simultaneous contact with the chemical substances within the drum, by inhalation and dermal contact, and with the chemical dusts generated while recharging the drums. In the case of a tannery which incorporates all the processes of leather production, beamhouse workers may also be exposed to the organic vapours generated in the finishing department; however, their exposure to these agents may be lower than that of those employed within the finishing area. Workers in the buffing area are exposed to leather dust and to its burden of tanning chemicals, while those working in the hide receiving and sorting area are exposed to hide dust. Buffing area workers may also be exposed to solvent vapours from the finishing area; due to the proximity of the hide-sorting area to the beamhouse, hide sorters may also be exposed to beamhouse contaminants. The chemical complexity of the tanning process and the wide variety of finishing agents used will almost certainly result in worker exposure via inhalation and dermal contact to multiple and changing chemical pollutants.

The industry is moving towards greater automation and mechanization. However, in many plants wet hides are still handled manually throughout the manufacturing process. Some workers may subject their hands and arms to tanning chemicals both by handling wet hides and by direct exposure to the chemicals.

It must be emphasized that often more than one of the operations are carried out in the same work room, and this results in cross pollution. Furthermore, in some operations, the work load and elevated temperature and relative humidity may change the environmental exposure. These features of the industry make evaluation of individual exposures difficult.

Employment in tanneries may entail exposure to a number of chemicals for which there is evidence of carcinogenicity in humans and/or laboratory animals (see Appendix 5, in this volume).

5.2 Evaluation

Very few epidemiological studies or case reports deal specifically with workers engaged in leather tanning and processing. There is no evidence to suggest an association between leather tanning and nasal cancer. The suggested associations between employment in the leather industry (not further specified) and cancer of the lung, larynx, buccal cavity, pharynx, and kidney and lymphomas come from hypothesis-generating surveys. They do not refer specifically to workers in tanneries. A positive association between employment in the leather industry (not further specified) and bladder cancer is supported by a number of studies. The only study that dealt specifically with leather tanners, however, revealed a relative risk of 1.5, which is not statistically significant.

Subsequent evaluation: Suppl. 7 (1987)


Last updated: 8 April 1998






















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