Michael Gilbertson

Breast cancer risk in relation to occupations with exposure to carcinogens and endocrine disruptors: a Canadian case–control study

BackgroundEndocrine disrupting chemicals and carcinogens, some of which may not yet have been classified as such, are present in many occupational environments and could increase breast cancer risk. Prior research has identified associations with breast cancer and work in agricultural and industrial settings. The purpose of this study was to further characterize possible links between breast cancer risk and occupation, particularly in farming and manufacturing, as well as to examine the impacts of early agricultural exposures, and exposure effects that are specific to the endocrine receptor status of tumours.Methods1005 breast cancer cases referred by a regional cancer center and 1146 randomly-selected community controls provided detailed data including occupational and reproductive histories. All reported jobs wereindustry- and occupation-coded for the construction of cumulative exposure metrics representing likely exposure to carcinogens and endocrine disruptors. In a frequency-matched case–control design, exposure effects were estimated using conditional logistic regression.ResultsAcross all sectors, women in jobs with potentially high exposures to carcinogens and endocrine disruptors had elevated breast cancer risk (OR = 1.42; 95% CI, 1.18-1.73, for 10 years exposure duration). Specific sectors with elevated risk included: agriculture (OR = 1.36; 95% CI, 1.01-1.82); bars-gambling (OR = 2.28; 95% CI, 0.94-5.53); automotive plastics manufacturing (OR = 2.68; 95% CI, 1.47-4.88), food canning (OR = 2.35; 95% CI, 1.00-5.53), and metalworking (OR = 1.73; 95% CI, 1.02-2.92). Estrogen receptor status of tumors with elevated risk differed by occupational grouping. Premenopausal breast cancer risk was highest for automotive plastics (OR = 4.76; 95% CI, 1.58-14.4) and food canning (OR = 5.70; 95% CI, 1.03-31.5).ConclusionsThese observations support hypotheses linking breast cancer risk and exposures likely to include carcinogens and endocrine disruptors, and demonstrate the value of detailed work histories in environmental and occupational epidemiology.

Sex Ratio Changes as Sentinel Health Events of Endocrine Disruption

Abstract The production and widespread use of synthetic chemicals since the 1940s have resulted in ubiquitous contamination of fish, wildlife and human populations. Since the 1960s, observers have documented major damage to wildlife reproduction across the globe, and subsequently, damage to reproductive health in exposed humans as well. The sex ratio in human communities and populations can be readily measured to ascertain whether reproductive effects, such as subtle birth defects of the reproductive tract caused by exposures to chemicals, might be occurring. Male to female sex ratios appear to be declining in populations in several parts of the globe, possibly as a result of prenatal exposures to chemicals. Sex ratio data for communities with unusual occupational or environmental exposures can be compiled using traditional epidemiological techniques in pursuit of environmental justice. Local, regional and national population health researchers and occupational hygienists can use health statistics to examine sex ratios as sentinel health events that might portend patterns of subtle structural birth defects of the reproductive tract and functional deficits in neurodevelopment.

Occupation and breast cancer: a Canadian case-control study.

Abstract:u2002 A local collaborative process was launched in Windsor, Ontario, Canada to explore the role of occupation as a risk factor for cancer. An initial hypothesis‐generating study found an increased risk for breast cancer among women aged 55 years or younger who had ever worked in farming. On the basis of this result, a 2‐year case–control study was undertaken to evaluate the lifetime occupational histories of women with breast cancer. The results indicate that women with breast cancer were nearly three times more likely to have worked in agriculture when compared to the controls (OR = 2.80 [95% CI, 1.6–4.8]). The risk for those who worked in agriculture and subsequently worked in automotive‐related manufacturing was further elevated (OR = 4.0 [95% CI, 1.7–9.9]). The risk for those employed in agriculture and subsequently employed in health care was also elevated (OR = 2.3 [95% CI, 1.1–4.6]). Farming tended to be among the earlier jobs worked, often during adolescence. While this article has limitations including the small sample size and the lack of information regarding specific exposures, it does provide evidence of a possible association between farming and breast cancer. The findings indicate the need for further study to determine which aspects of farming may be of biological importance and to better understand the significance of timing of exposure in terms of cancer risk.

Index of Congenital Minamata Disease in Canadian Areas of Concern in the Great Lakes: An Eco-Social Epidemiological Approach

Cerebral palsy is one of the symptoms of congenital Minamata disease associated with exposure to methyl mercury. Cerebral palsy hospitalization rates for 17 Canadian Areas of Concern have been used as a health index in evaluating the effectiveness of the United States and Canadian governments in implementing their Great Lakes Water Quality Agreement. Elevated rates in males in several locations was associated with historic uses of mercury and with natural sources indicating that the governments have failed to protect human health from exposures to this persistent toxic substance. Advances in epidemiological theory indicate that the reasons for this failure cannot be explained solely in scientific and technical frames but that the social, economic, and political contexts of the two nations need to be examined.

New bioindicators for mercury toxicological assessment: Recommendations from the first international bioindicators roundtable

Editors Note: At the 14th International Conference on Environmental Bioindicators (14th ICEBI) held in Linthicum Heights, Maryland, USA on 24–26 April 2006, the Conference Chairs and Program Committee initiated the Roundtable Discussion Groups as a prominent and regular feature of this and future conferences. The Discussions are designed to generate focused debate around key topic areas, led by academic, government and industry experts, and are structured to produce definitive papers for peer review and publication in EBIs first-quarter issues of each publication year. The three Roundtables of the 14th ICEBI posed questions revolving around the chosen topic areas of Mercury Bioindicators, Marine Ecosystem-level Indicators, and Regulatory and Policy Uses of Bioindicators, and moved from “what we know” to “where we need to go” and “what are the policy implications from our discussions and conclusions.” The paper on coral reef indicators was published in EBI 2(1) and was the first product of this undertaki...

Roundtable Discussion Groups Summary Papers: New Bioindicators for Mercury Toxicological Assessment: Recommendations from the First International Bioindicators Roundtable

Editors Note: At the 14th International Conference on Environmental Bioindicators (14th ICEBI) held in Linthicum Heights, Maryland, USA on 24–26 April 2006, the Conference Chairs and Program Committee initiated the Roundtable Discussion Groups as a prominent and regular feature of this and future conferences. The Discussions are designed to generate focused debate around key topic areas, led by academic, government and industry experts, and are structured to produce definitive papers for peer review and publication in EBIs first-quarter issues of each publication year. The three Roundtables of the 14th ICEBI posed questions revolving around the chosen topic areas of Mercury Bioindicators, Marine Ecosystem-level Indicators, and Regulatory and Policy Uses of Bioindicators, and moved from “what we know” to “where we need to go” and “what are the policy implications from our discussions and conclusions.” The paper on coral reef indicators was published in EBI 2(1) and was the first product of this undertaki...

New bioindicators for mercury toxicological assessment

Editors Note: At the 14th International Conference on Environmental Bioindicators (14th ICEBI) held in Linthicum Heights, Maryland, USA on 24–26 April 2006, the Conference Chairs and Program Committee initiated the Roundtable Discussion Groups as a prominent and regular feature of this and future conferences. The Discussions are designed to generate focused debate around key topic areas, led by academic, government and industry experts, and are structured to produce definitive papers for peer review and publication in EBIs first-quarter issues of each publication year. The three Roundtables of the 14th ICEBI posed questions revolving around the chosen topic areas of Mercury Bioindicators, Marine Ecosystem-level Indicators, and Regulatory and Policy Uses of Bioindicators, and moved from “what we know” to “where we need to go” and “what are the policy implications from our discussions and conclusions.” The paper on coral reef indicators was published in EBI 2(1) and was the first product of this undertaki...

Breast cancer and the environment: why research and preventive action are needed

The Editor n nCurrent Oncology n nJune 25, 2013 n nIn the February 2013 issue of Current Oncology, Dr. Steven Narod1 critiqued the 2012 study by Brophy et al.2, which found elevated breast cancer risk among several occupational groups. He also expressed skepticism concerning the role that environmental exposures to industrial chemicals and pollution play in the causation of breast cancer. That skepticism reflects an outdated epidemiologic analysis undertaken 30 years ago3. n nIn 2010, the President’s Cancer Panel in the United States drew attention to “the unacceptable burden of cancer resulting from environmental and occupational exposures,” which it said was “grossly underestimated.” The Panel stressed the need “to identify the many existing but unrecognized environmental carcinogens and eliminate those that are known from our workplaces, schools, and homes.” In Europe, attention has been drawn to the need to identify “hidden” groups whose occupational exposure to carcinogens is underrepresented in intervention strategies (European Agency for Safety and Health at Work. Workshop on Carcinogens and Work-Related Cancer. 2012). n nWorkers as a group tend to be more highly exposed to carcinogens, but they have been relatively neglected by epidemiologists. This lack of scientific attention could be characterized as a reflection of sex and class bias. The Brophy et al. study was conducted in response to those gaps. This comprehensive case–control study was considerably more than what Dr. Narod characterized as “an interesting pilot.” It was a hypothesis-driven study based on findings from two previous studies by the authors. Dr. Narod’s critique of the study design was also ill-informed. The authors acknowledge that there were social class differences between the cases and controls, just as there were exposure differences. That was precisely why the analysis carefully controlled for family income and education levels. Given the inevitable exposure misclassification, low-income (and generally more highly exposed) workers might be expected to show more residual excesses not accounted for in the exposure classification scheme used—as was observed. If participation rates were higher among non-cases in the service sector, as suggested by Dr. Narod, there should have been a nonspecific general excess across all manufacturing sectors—which was not observed. Most minor non-plastics sectors had deficits similar to those observed in services (liquor, tobacco, wood, printing, petroleum, glass and ceramic, electrical, jewellery and furniture) and in transportation. Differences in participation rates of controls would not generate higher estimated relative risks when cases are restricted by receptor type or menopausal status, as was observed. n nA strength of the Brophy et al. study was the compilation of detailed work histories that permitted systematic classification of jobs in broad exposure terms relating to carcinogens and endocrine-disrupting chemicals. Determining which chemicals and related mixtures to study is indeed a challenge, and that is why a study that identifies clear specific excess cancer is so valuable: it narrows the field. The findings point to very specific and practical next steps in exposure assessment, such as retrospectively describing the components of automotive plastics and canning polymers that were in use over the past 40 years in the study area’s automotive and food industries. n nDespite the paucity of scientific interest in occupational and environmental causes of breast cancer, a growing body of evidence is indicating elevated breast cancer risk associated with exogenous exposures. For example, Health Canada recently contributed to epidemiological research about the relationship of breast cancer with exposures to traffic pollution4. Dr. Issac Luginaah and colleagues5 identified 5 counties in southern Ontario and 2 areas in Toronto with “clusters” of breast cancer. Those findings supported the “hypothesis that breast cancer in southern Ontario may be associated with industrial and environmental (such as pesticides) pollutants” postulated by the researchers. As documented in the Brophy et al. paper, numerous national and international studies have identified occupational associations with breast cancer. Women’s occupational exposures to carcinogenic and endocrine-disrupting chemicals have recently been documented in work environments such as automotive plastics manufacturing6. n nDr. Narod asks “What is left to learn?” Perhaps we need to learn how we should respond to the increasing evidence. In the mid-1960s, during the debates between the tobacco industry and governments about the carcinogenicity of cigarette smoke and lung cancer, the United States Surgeon General and Sir Austin Bradford Hill produced guidelines for inferring causality. By finally applying those guidelines to the evidence concerning breast cancer and environmental exposures, a robust relationship is developing. Public health communities and governments should respond to the breast cancer epidemic by drawing on this growing body of knowledge and adopting bold initiatives at the political level. n nMore epidemiologic research on environmental causes of breast cancer should be conducted. Dr. Narod correctly points out that much of the information available about mammary carcinogens is derived from animal studies7. However, “affixing monitors to the lapels of women” to determine exposures over extended periods of time would not be practical or effective. It would be even less adequate for the study of breast cancer, in which endocrine and reproductive status may be important factors. Given the relative neglect of occupational epidemiology, particularly considering exposures to mixtures, the evidence from animal experimentation becomes vital for worker protection. The International Agency for Research on Cancer accepts that, “in the absence of adequate data on humans, it is biologically plausible and prudent to regard agents for which there is sufficient evidence of carcinogenicity in experimental animals as if they presented a carcinogenic risk to humans”2. n nAt the scientific and technical levels, the breast cancer epidemic is a crisis of modernity, with most cases unaccounted for by “known” risk factors. The U.S. Interagency Breast Cancer and Environmental Research Coordinating Committee recently put forward a science policy document on breast cancer, stressing primary prevention through reduction of exposures to chemicals. Equally, the breast cancer epidemic has generated a lack of confidence in our medical and public health institutions. Over the past 30 years, our governance, academic, publishing, and health institutions have become progressively beholden to corporate interests, thereby further undermining worker and consumer trust in the medical and public health authorities8. It is long past time that these institutional failings be addressed.