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Multiphasic health testing was provided to 744 rubber workers at a tire manufacturing plant. Sixty-two white males from this population had worked longest in the curing department. Personal exposure to respirable particulates was measured for curing press operators. Outcome on screening tests for curing workers was compared with that of 280 white males at this same plant who had never worked in departments known to include jobs where they could have been exposed to respiratory health hazards. Employment in the curing department is associated with shortness of breath, chest tightness, wheeze, loss of FEV-1 and FVC, decline of FEV-1/FVC, and tingling and numbness in the extremities. These associations are stronger with increased duration of employment in the curing department. This paper further demonstrates the potential for using multiphasic health testing combined with measurements of workplace exposure for identifying occupational health hazards.

A matched case-control study was conducted for 72 cases of leukemia occurring among employees of four rubber and tire manufacturing companies during the period from 1964 to 1973, to determine if certain environmental exposures were related to the risk of developing leukemia. Earlier studies conducted in one company had shown an association of lymphatic leukemia with a work history of possible solvent exposure, and the results of the present study suggest that the association is weaker than previously described. However, recently acquired detailed environmental information reported elsewhere tends to support the initial finding at this company. Further studies are required to fully resolve this issue. A finding was the lack of association in the order three companies. In addition, lymphatic leukemia was found to be associated with work experience in general service jobs for the two larger companies from which a majority (89%) of the cases derive. Intervals from exposure death peaked at 27 to 38 years. No elevated risk for myeloid leukemia was found.

Multiphasic health testing (MHT) is often offered to populations of workers usually with the objective of identifying individuals who may be ill. Results are typically not analyzed in relation to estimates of workplace exposure. We describe the results of combining MHT with industrial hygiene assessment of workplace exposures as a method of identifying possible health hazards rather than merely potentially ill individuals. MHT was offered to all production and maintenance workers employed at a tire manufacturing plant. Of 954, 744 participated. We measured worker exposure to respirable particulates, solvent vapor, and noise. We computed the frequency of positive screens among workers classified by exposure and compared these frequencies with expected values adjusted for confounding variables including age, sex, race, and smoking and drinking habits. Workers exposed to higher concentrations of respirable particulates exhibited signs of respiratory and gastrointestinal morbidity. Workers exposed to emissions from heated, uncured rubber undergoing plastic deformation reported chest tightness on return to work. We conclude that combining MHT with assessment of workplace exposure is a valid method for identifying possible occupational health hazards.

The pulmonary function and symptoms of 125 workers exposed to carbon black in dry cell battery and tire manufacturing plants were investigated. There was no significant difference in the pulmonary function of the subjects in the two plants. There was good agreement in the symptoms reported in the two different factories: cough with phlegm production, tiredness, chest pain, catarrh, headache, and skin irritation. The symptoms also corroborate those reported in the few studies on the pulmonary effects of carbon black. The suspended particulate levels in the dry cell battery plant ranged from 25 to 34 mg/m3 and the subjects with the highest probable exposure level had the most impaired pulmonary function. The pulmonary function of the exposed subjects was significantly lower than that of a control, nonindustrially exposed population. The drop in the lung function from the expected value per year of age was relatively constant for all the study subgroups but the drop per year of duration of employment was more severe in the earlier years of employment. This study has underscored the need for occupational health regulations in the industries of developing countries.

A retrospective follow-up study was conducted to evaluate mortality and cancer incidence between 1954 and 1976 among 1,792 white male production workers employed for at least 2 years at a tire manufacturing plant. There were no marked excesses in overall or site-specific cancer deaths or incident cases. Compared to U.S. white males, men employed for at least 10 years experienced small increases in deaths from cancers of the large intestine, pancreas, and lung. Results obtained by comparing observed incident cancer cases to the numbers expected based on age- and calendar time-specific incidence rates of Connecticut males also suggested excesses of these three malignancies. These findings were based on small numbers and therefore do not necessarily indicate causal associations between cancer excesses and employment in the rubber tire industry. However, because the workers studied comprised a relatively young population that may not have experienced the full impact of carcinogenic occupational exposures, further follow-up is warranted.

Since 1963 the observed mortality experience of BCNS cancers among rubber workers appears to be very comparable to that expected. A possible exception to this statement is the experience of one plant in Akron, Ohio, reported by Monson and Nakano. Excesses in earlier years may also be localized to one or two companies. The results of a case-control study did not support a hypothesized association of elevated BCNS cancer risk with exposures in the tire building/tire assembly segments of the rubber tire manufacturing process. The direction of future epidemiologic studies would benefit by the assembly of as large a number of cases as possible and should focus on calendar periods of exposure, make allowance for a latent period, and include retrospective industrial hygiene assessments of the specific exposures.

Publisher Summary This chapter focuses on recent findings about the possible health risks to workers in an industry using both natural and synthetic rubber as its basic materials. The India Rubber Regulations of 1922 laid down the conditions and duties of employers who hire people to work with lead and in fume processes. The fume processes were related to exposure to solvents, including carbon bisulfide, sulfur chloride, benzene, carbon tetrachloride, and trichloroethylene. Later, the 1955 India Rubber Regulations prohibited the use of carbon bisulfide. The physical labor imposed by the nature of work in the rubber industry commonly leads to muscular strains and sprains, tenosynovitis, and, especially, back injuries. In tire manufacturing, there is exposure to rubber solvents and solutions. However, it is during tire curing that the greatest potential for exposure to fumes exists. Depending on work practices and the plant layout, men employed as molders, sprayers, and inspectors may be exposed to fumes at the final stage of processing. Long-term health and safety can be assured by sound engineering practices, continued epidemiological surveillance, and environmental monitoring. These practices ensure compliance with standards. Health and safety in this context imply freedom from the risk of acute illness, injury, or long-term disease caused by the work environment.

The aim of an ergonomics intervention conducted in the tire manufacturing industry was to improve working conditions. Before the start, a senior manager supported the intervention. Participants were divided into teams and trained. After observing the overall performance of the teams, over 100 improvements were successfully implemented. After the improvements, there were statistically significant differences in annual and weekly prevalence of, and annual disability reported for, the upper back, the lower back, knees and wrists between before and after intervention. The annual prevalence of upper back, lower back, knee and wrist complaints decreased from, respectively, 60.3%, 50.2%, 28.9%, 25.8% before the intervention to 31.3%, 35.9%, 17.1%, 20.7% after the intervention. Significant factors were training and supportive environment based on full commitment of the top management.