Nested Case-Control Study of Lung Cancer Among Chemical Workers

Abstract

A recent cohort mortality study of 19,608 male employees of a major Texas chemical production facility had suggested that they might be at higher risk of lung cancer compared with the male population of the United States or Texas but not with the male population of the five-county area in which they reside. An occupational exposure was a possible explanation for this pattern, and a nested case-control study was undertaken of the 308 lung cancer deaths observed between 1940 and 1981. Two control groups, one a decedent and the other a "living" series, were individually matched to cases one-for-one. Interviews were conducted with subjects or their next of kin to collect information on smoking and other potential confounders. These data were combined with employee work history records and industrial hygiene data to form the basis of the analyses. Traditional stratification methods and conditional logistic regression were employed to examine for effect modification and to control confounding. Statistically significant, positive and negative associations were found for assignment to several work areas within the facility. Suggestive associations were observed for exposure to sulfur dioxide and heat. These and additional associations are discussed relative to evidence from other studies.

Formaldehyde exposure and respiratory cancer--a meta-analysis of the epidemiologic evidence.

“…In place of unlagged values for lung cancer, lagged equivalents were extracted from the repo rts of Blair et al (7) on United States (US) workers producing and using for malde hyde , Bond et al (8) on Dow Chemical (Texas) workers, and Stayner et al (9) on US garment workers exposed to formaldehyde . For the exposure-res ponse ana lyses in the large mortality study by Blair et al (7), low-med ium forma ldehyde exposu re referr ed to any nonzero expo sure up to 5.5 ppm-years, and any expos ure exceeding 5.5 ppm-years was considered substantial.…”

Epidemiologic evidence on the relationship between formaldehyde exposure and cancer.

“…In most of the other case-referent studies industrial hygienists classified the jobs held by subjects into semiquantitative cat egories (41,42) or nominal categories (43)(44)(45). Estimates of possible level of expo sure were not made .…”

“…Estimates of possible level of expo sure were not made . In man y cases the subjects were exposed to other chemicals, including known or potential carcinogens (41)(42)(43)(44)(45). One study had two industrial hygienists independently evaluate expo sure, and risks of nasal cancer were calculated on th e basis of each assessment (42) .…”

“…showed higher risks with shorter latency (34,43,50). Risk of lung cancer by level or duration of expo sure to formaldehyde is shown in table 8.…”

Assessment of the effect of occupational exposure to formaldehyde on the risk of lung cancer in two Canadian population-based case–control studies

“…Some of the older studies used job title (often embalmers or pathologists) as a proxy for exposure (8, 14-17, 19, 21) or a more elaborate job exposure matrix (JEM) but focused on the last job held as indicated on the death certificate (27). Other methods included the use of (i) employment records (2,6,7,9,10,12,13,18,22,25,26), (ii) a JEM, (iii) industrial hygiene data (2,6,10,18,22,23,25,26), or (iv) selfreport of exposure to formaldehyde (11,20,24) or occupational history (23,28). Information on smoking, a key potential confounder, was available and accounted for in the analyses in only seven studies (6,11,20,22,24,25,28), some of which had large proportions of missing values for smoking variables.…”