An updated study of mortality among North American synthetic rubber industry workers.

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An updated study of mortality among North American synthetic rubber industry

workers.

E Delzell, N Sathiakumar, J Graff, M Macaluso, G Maldonado, R s, and

Health Effects Institute

Res Rep Health Eff Inst, August 1, 2006; (132): 1-63; discussion 65-74.

Department of Epidemiology, School of Public Health, 1665 University Blvd,

University of Alabama at Birmingham, Birmingham AL 35294-0022, USA.

This study evaluated mortality rates from leukemia and other diseases during the

time period 1944 through 1998 among 17,924 men employed in the synthetic rubber

industry. In this group, there were 6237 deaths, which is 14% fewer than the

7242 deaths expected based on general population rates. Numbers of observed

versus expected deaths (shown hereafter as observed/expected) were 1608/1741 for

all cancers combined, including 71/61 for leukemia, 53/53 for non-Hodgkin

lymphoma (NHL*), and 26/27 for multiple myeloma. The higher than expected number

of deaths from leukemia (16% increase) was concentrated in workers paid hourly

who had started work 20 to 29 years earlier, had worked 10 or more years in the

industry, and had worked in subgroups employed in polymerization, coagulation,

maintenance labor, and laboratory operations. The overall higher leukemia

mortality rate, as well as the higher rate in the subgroup of hourly workers who

had 20 or more years since hire and 10 or more years worked, was not limited to

a particular form of leukemia. Cumulative exposure to 1,3-butadiene (BD) was

associated positively with all leukemias, with chronic myelogenous leukemia and,

to a lesser extent, with chronic lymphocytic leukemia (CLL). Exposure to styrene

or to dimethyldithiocarbamate (DMDTC) also was associated positively with

leukemia. Exposures to these two agents were correlated with exposure to BD;

data were limited on the independent effects of each of the three chemicals on

leukemia. After controlling for the effects of BD, we found no consistent

exposure-response relation between either styrene or DMDTC and all leukemias,

chronic myelogenous leukemia, or CLL. However, a positive association between

any exposure to DMDTC and leukemia persisted. The data from this study indicate

that employment in the synthetic rubber industry is related causally to

leukemia. Uncertainty remains about the specific agent or agents responsible for

the association. The carcinogenic mechanisms through which BD, styrene, or DMDTC

could cause leukemia in humans have not been established, and epidemiologic

support for a leukemogenic role is limited for these agents. Styrene and DMDTC

were associated positively with NHL. External support for this relation has not

been reported from other epidemiologic studies. The study did not find any clear

relation between exposure to BD, styrene, or DMDTC and multiple myeloma. Some

subgroups of subjects had more than the expected number deaths from colorectal

cancer, prostate cancer, and other diseases. These increases did not appear to

be related to occupational exposure in the industry.

PMID: 17326338