Cancer in the Auto Industry

A Map of the Literature for the
Industrial Disease Standards Panel (Occupational Disease Panel)

by Donald C. Cole MD MSc FRCP(C)
Final version July 1994

Contents

I Introduction

II Methods

III Results

IV Discussion

V Recommendations

VI References

Tables

1. Studies reporting increased cancer risk for workers in motor vehicle/transportation equipment production as an industry

2. Workplace studies reporting relationships between plants/operations and cancer (all on US males unless noted otherwise)

3. Occupation/job focused studies (mechanics & pattern makers) and specific relationships within table 2 studies

4. Summary of positive associations found in tables 1-3

5. Exposure-cancer relationships in table 1-3 studies (plus Tolbert's review)

6. Studies reporting additional potentially carcinogenic exposures in the auto industry

7. IARC rating of potential exposures in the auto industry and these exposures' presence in the Ministry of Labour exposure database

I. INTRODUCTION

Concern over possible relationships between work in the North American auto industry and cancer has been ongoing over the last two decades. Since the early 1980's, considerable research on these relationships has been conducted, much of it under the bipartite direction of the United Auto Workers and the Big Three companies. Attention has also been directed to consolidating this research to inform policy, first to promote reduction of workplace exposures (NIOSH warnings about cutting fluids in the 1970's) and more recently to consider compensation of those workers whose cancers may be attributable to past exposures in the auto industry. The Industrial Disease Standards Panel (IDSP) of the Ontario Ministry of Labour commissioned reviews of the health hazards of occupational exposure to cutting oils (Tolbert 1993) and of the association of stomach cancer and occupation (Stock 1993), which both included studies on the auto industry.

The IDSP commissioned this review to provide a "map" of relevant epidemiological literature on cancer and carcinogenic exposures in the auto industry. It is a map which sets out a number of potential exposure-cancer associations, beyond those already identified for cutting oils. It is not a systematic overview employing critical appraisal methods to judge the evidence for causation of any one of the reported relationships. Nor is it a feasibility project to coordinate with the relevant stakeholders and document the possibilities of initiating research on cancer in the auto industry in Ontario. These two latter options will be considered in the discussion and recommendation sections below.

II. METHODS

Setting the boundaries for the auto industry was difficult given the huge array of basic manufacturing and parts industries that supply the auto industry and the huge range of post assembly services oriented towards the automobile. The core group of occupations in the Canadian Standard Occupational Classification (SOC) are: 8513 Motor Vehicle Fabricating and Assembling Occupations and 8511 Engine and Related Equipment Fabricating and Assembling Operations. One could construe the core Ontario Workers' Compensation Board Rate Groups as: 419 Motor Vehicle Assembly Industry, 420 Motor Vehicle Engine and Parts Industry, 421 Other Motor Vehicle Parts/Equipment and 424 Motor Vehicle Stampings Industry. In addition there are: 425 Motor Vehicle Wheels and Brakes, 428 Motor Vehicle Fabric Accessories Industries, 432 Truck and Bus Body Industry, 433 Commercial Trailer Industry and 438 Recreational Vehicle and Trailer Industry. Studies included occupations other that those cited in the SOC but part of the core WCB rate groups (and hence the Standard Industrial Classification). Some studies likely included industries outside the core WCB rate groups. However, no attempt was made to exclude those not in the core WCB rate groups nor was literature on other related industries (eg. fabric accessories industry, tire industry) specifically sought as it was thought to be outside the scope of this review.

IDSP staff and members provided copies of previous literature searches, reports, names of researchers and potentially relevant articles. Perusal of these materials and contact with several researchers permitted the construction of a mailing list of 108 contacts in North America, Europe and Asia. Letters outlining the purpose of the review and requesting assistance in obtaining reports on research were sent to each of the contacts. Twenty-nine responses were obtained from researchers in North America and Europe. Most were supportive of the need for a review and some provided additional studies to those known to the reviewer. Some researchers noted studies of relevance that had been initiated but not completed and other studies in which results remained with the corporate sponsor and were unavailable. Hence a publication bias likely exists in the material quoted for this review.

Two computerized bibliographic literature searches were carried out. MEDLINE on compact discs was searched from years 1981-1994 using the following search strategy: air-pollutants-occupational or occupational-exposure or occupational diseases or occupational medicine and neoplasms and auto* or automob* or automot* or motor vehicle* or car* or auto indust* or general motor* or ford or chrysler. Over 100 citations were obtained, the majority relevant. NIOSHTIC on Dialog was searched using the following search strategy: automobile()industry or motor()vehicles or auto* or auto parts and carcinogen* or neoplasia or cancer. Twenty-eight citations were obtained, almost all relevant. The majority of citations from both searches were of studies already known to the reviewer but over 10 new reports were obtained.

Extended case series, such as that inplicating eye cancer among automobile industry workers (Lane 1937), were excluded. Case-control, proportionate mortality and cohort designs were included. The comparison populations (eg. other adults in the state or country, workers in other parts of the plant) and the summary measures of association (eg. proportional mortality ratio, odds ratio, standardized mortality ratio) differ between these types of studies. An extensive debate exists about the extent to which biases can affect them, particularly the healthy worker effect (Park et al 1991). For inclusion, studies had to contain significant positive findings (using p<.05), irrespective of the power of the study to detect such differences and despite the fact that a number of studies suffered from small sample sizes (eg. Chiazze 1980). This conservative approach was taken initially because the population studies described themselves as hypothesis generating with multiple comparisons of association between industry or occupation and cancers. In order for them to be retrieved in the search process, elevations of risk would have to be found and noted in the abstract. Those hundreds of other studies which broadly examine occupation or industry and cancer but did not find an association for our sector of interest would therefore be excluded. The approach to significance was extended to the workplace studies because of the decision to only highlight positive findings rather than the range of results showing no association. Consideration of all the studies which provide information on a particular relationship, greater examination of study design, measurement and analysis issues, explicit consideration of the role of confounders (Andejelkovich et al 1992) and consideration of the range of other evidence (toxicological, hygiene, etc) contributing to a judgement of causation would be part of a systematic overview of any particular association noted in tables 2-4 below..

In addition, IDSP staff conducted a search of the Ministry of Labour's hygiene monitoring data base for results of sampling for carcinogens in companies forming part of the auto industry in Ontario. The purpose was to assess the state of readily available exposure data and ascertain if possible the relevance of the potentially carcinogenic exposures reported in the literature. Unfortunately the database only has data since the mid 1980's which severely limits retrospective exposure assessment (IJE 1993). Its value may better lie in supporting prospective work on the rapidly changing technology and exposures in the sector (see discussion & recommendations).

III.RESULTS

In reporting the results, a broad distinction can be made between those studies which start with cancer cases in the population and then seek information on occupation (eg. Hall & Rosenman 1991) and those which define a population as working for a company (eg. Delzell et al 1993), at a particular workplace (eg. Silverstein et al 1986) or in a particular occupation (eg. Demers et al 1985) and then examine proportions or rates of cancer in that working population. Those starting with cancer cases or the employees of a large company can provide information on the general relationship between working in the auto industry and cancer (table 1). Those focusing on workplaces are best at informing us on the relationship between specific plants/operations and cancer (table 2). They can often provide us the most information on specific occupations (table 3) and exposures (table 4) although occupation based studies also provide such information (particularly table 3).

Table 1 sets out a number of studies with increased cancer rates among motor vehicle manufacturing workers in three different continents and across both sexes. Occupation information for these studies came from hospital medical records (Hall et al 1991), interview (Silverman et al 1989, Cordier 1993 & Wu-Williams 1993) or company computerized personnel records (Delzell et al 1993). The tendency of all but Delzell and colleagues work to report only on the positive associations between cancer and a particular industry should be remembered (see Methods discussion).

None of the Table 2 studies would be prone to this retrieval bias because they were explicitly carried out on motor vehicle related workplaces or companies. Missing from table 2 is a study which did not demonstrate increased cancer risks in the plastic composites industry but which included automotive parts production with styrene exposure (Coggan et al 1987).

Table 2.2        Workplace studies reporting relationships between plants/operations and cancer                         (all on US males unless noted otherwise) (cont.)
Plants or   Operations	Body System with Cancer
	Digestive	Genito-   urinary	Lymphatic	Respiratory
Engine   Engine   & foundry   Foundry   Stamping	Liver (PMR=2.61)   & pancreas   (PMR 1.89) in   whites (Vena et al   1985)   Stomach   (SMR=158) in   whites & pancreas   (SMR=303) in   blacks (Rotini et al   1993)   All (SMPR=226)   in whites   (Silverstein et al   1985b)   Stomach   (SMR=4.41,   PMR=6.76) (Park   et al 1994)	Bladder   (PMR=2.28   ) (Vena et al   1985)   Prostate   (SMR=234)   in blacks   (Rotini et al   1993)	Leukemia   (SPMR=284   ) in whites   (Silverstein   et al 1986)   Leukemia   (SPMR=428   ) in whites   (Silverstein   et al 1985b)	All (PMR 1.27)   (Vena et al 1985)   Lung   (SPMR=148) in   whites   (Silverstein et al   1986)   Lung (SMR=132)   in non-whites   (Andjelkovich et   al 1990 & 1992)   Lung (SPMR=   220) (Silverstein   et al 1985b)
SPMR   standardized proportional mortality ratio

Table 3 includes findings from three sources: analyses of the Table 1 studies by occupation rather than industry (eg. Silverman et al); sub-analyses on the jobs found in table 2 studies (eg. Dhara et al); and studies focusing on particular occupations (eg. Tilley et al). Significance requirements were relaxed for the sub-analyses of table 2 studies in order to assist the process of indentification of jobs potentially at higher risk. However, some sub-analyses reported separately, such as Chiazze and colleagues paper on spray painters (1980), did not calculate confidence intervals nor report significance but examine relationships across years of exposure strata (as well as non-significant results because of small numbers of cases), indicating the additional kinds of information that should be considered in any judgements about causality.

Table 3.1        Occupation/ job focused studies (mechanics & pattern makers) and specific                         relationships within table 2 studies
Occupa-   tions/Jobs	Body System with Cancer
	Digestive	Genito-urinary	Lymphatic	Respiratory
Main-   tenance   Mechanics-     repairmen   Millwright/   Welder	Pancreas (PMR=2.81     for >0.5yrs, 2.68 for   >5yrs & 4.29 for   >10yrs) (Dhara et al   1990)   Stomach (MOR=4.7)   (Park et al 1994)   All digestive   (SPMR=1.77) in   blacks, esophageal   (SPMR=3.87 for    5yrs & 5.29 for    10yrs) & rectum   (SPMR=4.20 for    5yrs & 4.53 for    10yrs) in whites   (Park et al 1986)   All digestive   (OR=16.5 in 40+ at   death (Silverstein et   al 1985b)	Bladder (OR=10.2)   in whites in trucking     (Silverman et al   1989)   Wilm's tumour in   offspring (OR=   10.39 for exposure   during pregnancy &   11.44 for postnatal   (Olshan et al 1990)	Lympho-   poietic   (SPMR=   3.03) in   blacks (Park     et al 1986)	Lung   (SMR=170)   (Järvholm et al   1988)   Lung (OR=13.2     in 40+ at death)   (Silverstein et   al 1985b)
MOR    mortality odds ratio

Table 3.2       Occupation/ job focused studies (mechanics & pattern makers) and specific                        relationships within table 2 studies (cont.)
Occupa-   tions/Jobs	Body System with Cancer
	Digestive	Lymphatic	Respiratory	Other
Pattern   makers   Spray   painters   Tool & die     makers   Welders	Colon (SMR=2.0) (Tilley et al   1990)   Colorectal polyps (OR 1.9)   (Demers et al 1985)   Stomach (SMR=1.2) & colon   (SMR=1.6) in whites (Roscoe et al   1992)   Unspecified digestive (SMR=3990)     (Becker et al 1992)   Pancreas (PMR=3.85 for >10yrs   (Dhara et al 1990)   Stomach (MOR=2.9) (Park et al   1994)	Lympho-   poetic   (PMR=4.9)   (Silverstein     et al 1988)	Lung   (MOR=2.7)   (Park et al   1994)	Brain &   CNS   (SMR=   667)   (Becker et   al 1992)   Various   cancers   (PMR's up   to 4.9)   (Chiazze et     al 1980)

Table 4 summarizes the kinds of cancers associated with work in the sector from tables 1-3. Every effort was made to not double count the studies so that each report is for a separate population-cancer relationship.

Exposures which researchers have implicated in these associations are set out in table 5. Some of these conducted hygiene monitoring and found high levels in work areas associated with high cancer rates (eg. PAH's in Silverstein et al 1985b). Most are based on a general body of literature on exposure (eg. asbestos in Järvholm et al 1988, ). Tolbert's review on cutting fluids is cited to refer to several studies which implicate several cancers, but details are not provided to avoid redundancy with her and subsequent cutting fluids work well known to the IDSP (OHCOW 1994).

Table 6 sets out other studies which provide exposure information that may account for the occurrence of cancer in automotive industry (eg. benzene in Aksay et al 1987 could account for lymphatic cancer increases).

In the left hand column of table 7 are exposures which are likely to occur in the auto industry that IARC has classified on carcinogenicity. In the right hand column are results from the Ministry of Labour exposure database. Of note is that some relatively recent exposures to recognized carcinogens have been over current Ontario guidelines.

IV. DISCUSSION

Across the tables, one can see a wide variety of cancers, potentially indicating either that multiple exposures (eg for spray painters) or potentially potent carcinogens (eg. coal tar pitch volatiles) are affecting different body systems. Some relationships are consistent with known carcinogenic industrial operations (eg. foundries with lung cancer for DOFASCO workers) or carcinogenic exposures (eg. asbestos) already recognized in Ontario. Those related to cutting fluids have been dealt with by the IDSP in depth over the last year but it is unlikely that they alone account for all of the relationships found in the table 4. Some relationships such as digestive cancers among pattern makers have been the subject of ongoing controversy over the evidence (Ernster 1992). Yet there remain a number of associations between cancers and operations, occupations or exposures that remain to be explored or confirmed (eg. lymphatic cancers in assembly operations). Similarly some exposures over which some concern was expressed to this reviewer such as fumes from plastics operations have not been extensively investigated in the auto industry although suggestive evidence exists in literature on other industries (eg. polymer extrusion fumes and solvents linked with lymphatic leukaemias in Ott et al 1980).

In the Ontario context, documentation of cases of cancer is relatively easy because of the Ontario Cancer Registry. An ongoing challenge in interpreting increased risks for cancer is the documentation of historical exposures both at the workplace and from personal habits. A combined European effort took place to improve retrospective exposure assessment (IJE 1993). In a recent conference, the range of success in achieving adequate exposure information and some innovative strategies were explored (IARC 1994). A number of innovative ways to document exposures have been forthcoming in studies on the motor vehicle sector. Park and colleagues (1991) describe a way of working with workplace partners which relies on the latters' experience to help reconstruct historical exposures. Macaluso and colleagues (1993) used a survey approach for documenting solvent use and potential worker exposure in the motor vehicle manufacturing industry as a whole. Response rates were poor but clear gradations of exposure by facilities and departments could be documented from a wide range of sources. McCammon and colleagues (1985) characterized current exposures in automotive wood model shops using a range of standard industrial hygiene monitoring techniques. Mygind and colleagues used manufacturers data sheets to construct a profile of chemical exposures in auto repair and body shops. The Finnish Institute of Occupational Health (Alho et al 1988) developed an registry of exposure to carcinogens which included painters in motor vehicle manufacturing operations among a range of other industries.

These range of techniques to obtain a clearer picture of both historical and current exposures are becoming integral to the IARC sponsored studies of cancer in particular industrial sectors. Factors which support international collaboration on cancer in the motor vehicle manufacturing sector are: the global nature of the industry; the potential variations in intensities of exposure from those in the US; the existence of sound cancer registries in other jurisdiction, particularly Scandinavia; and the size of the international workforce would allow sufficient power to detect significant exposure-cancer relationships in sub-analyses by occupations, departments and specific exposures. It is time for greater extension of research activity beyond the US which has made the major contributions to date.

Such international collaboration with concomitant exposure documentation would not only assist the interpretation of evidence on risk for cancer but also have other purposes. At a social policy level, it permits the systematic assignment of a proportion of cancers attributable to particular occupations (Vineis et al 1991) which would contribute to the primary prevention of cancer (eg. recently convened Ontario task force). In Finland, the carcinogen data base resulted in targeted reduction in use of some carcinogens, as has occurred for asbestos and is being considered with respect to cutting fluids in Ontario. In the United States, cancer-exposure documentation facilitated the upgrading of equipment with concomittant reduction in exposures (Silverstein et al 1985b) and facilitated workplace cancer control education programs which resulted in local reductions of exposure to carcinogens (Silverstein et al 1987).

V RECOMENDATIONS

On the basis of this document and the above discussion, I would suggest the following avenues of activity for the IDSP:

To improve Ontario information:

1. Explore collaborative development of data-bases, both employee-job based and exposure-department based, with companies and unions in the motor vehicle manufacturing sector and appropriate Ontario research units or organizations (eg. Ministry of Labour, Institute for Work & Health, universities)
2. Explore expansion of the Ministry of Labour exposure data base to include more historical information and expand existing information on priority areas (eg. table 2 operations or where substances from tables 5-7 have been or are used)

To improve international information:

3. Approach IARC re international coordination of an industry based study.
4. Consider collaboration across North America via the Labour Commission which has been created by the side agreements.

To fully document associations showing considerable consistency in the literature:

5. Conduct an overview of lung cancer and foundry work across all industrial sectors including the auto industry.

To move ahead on recognized associations:

6. Proceed with work on the recognition of cancers related to cutting fluids exposure.

To support exposure reduction initiatives:

7. Share this review with workplace partners for support in implementation of toxics use reduction initiatives, such as is being considered for cutting fluids.

To support education initiatives:

8. Share this review with workplace partners, the Canadian Cancer Society and the Workplace Health and Safety Agency for consideration in cancer prevention education initiatives.

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