Historical perspectives of occupational cancer

Role of Occupation in Shaping Cancer Disparities

Simple Summary

The investigation of cancer disparities is of major importance. In this paper, we address this issue through the occupational point of view, trying to capture how work and its related factors impact on cancer inequalities. The data we provide may increase awareness relevant to cancer control, and stimulate further studies aimed at the identification of the occupational determinants of cancer disparities and the quantification of their role.

Abstract

Cancer occurrence is characterized globally by profound socioeconomic differences. Occupation is a fundamental component of socioeconomic status. In this review, we discuss the role of occupation as a determinant of cancer disparities. First, we address the issue of participation in cancer screening programs based on income, health insurance, occupational status and job title. Second, we review the role of occupation in contributing to disparities by acting as a mediator between cancer and (i) education and (ii) race/ethnicity. Lastly, we analyze data from a multicenter case−control study of lung cancer to calculate the mediating role of occupational exposure to diesel exhaust, silica and welding fumes in the association between education and lung cancer. By addressing the complex paths from occupation to cancer inequalities from multiple points of view, we provide evidence that occupational-related characteristics, such as income, health insurance, unemployment and hazardous exposures impinge on cancer control and outcomes. The increasing awareness of these aspects is fundamental and should lead to public health interventions to avoid inequalities rising from occupational factors.

In vitro genotoxicity studies using complex hydrophobic mixtures: efficient delivery of a petroleum sample to cultured C3H/10T1/2 cells via lipid vesicle incorporation

Petroleum fractions are a diverse group of extremely hydrophobic mixtures, some of which display strong carcinogenicity in animal skin painting experiments. Interpretation of in vitro genotoxicity experiments with these samples is complicated by inefficient delivery of these hydrophobic substances inside target cells. We therefore developed methods to assess and improve the efficiency of delivering a petroleum sample (Matrix, A.P.I. 81-17) to cultured C3H/10T1/2 cells for genotoxicity studies via lipid vesicle incorporation. Three radiolabeled compounds (14C-benzo(a)pyrene, 14C-decane, and 14C-naphthalene) of widely differing volatilities, broadly representative of the spectrum of compounds in petroleum samples, were separately added to Matrix. Lipid vesicles containing Matrix and radiolabeled compounds were prepared by the classical methods for preparing neutral, positive, and negatively charged multilamellar and unilamellar liposomes. Of these, the classical methods for preparing neutral unilamellar liposomes were the most successful for delivering radiolabeled compounds in Matrix to cells. Vesicles optimal for the delivery of tracers in Matrix were prepared with DSPC:cholesterol:lyso-PC (8.8:0.8:0.4, molar ratio) in a Matrix to lipid ratio of 31:69 (w/w). This new method of delivery resulted in proportional, dose-dependent, and reproducible uptake of all tracers. Further, cells treated with this preparation took up 2.5-fold more 14C-decane, 1.5-fold more 14C-BaP, and 18-fold more 14C-naphthalene added to Matrix than did cells treated with Matrix emulsified in tissue culture medium. In contrast, tracers were not taken up in a proportional or reproducible manner when emulsions were used, and in fact, uptake of 14C-naphthalene was consistently very small. Two petroleum fractions, C(2)029188 and C(3)029194, were 4- and 6-fold more cytotoxic, respectively, when delivered to C3H/10T1/2 cells by lipid vesicles than emulsions. The carcinogenic petroleum fraction C(5)0292202 induces type II transformed foci in C3H/10T1/2 cells when cells were treated with C(5)0292202 incorporated into lipid vesicles. The methods for lipid vesicle incorporation described here are effective in delivering hydrophobic petroleum fractions to cells and provide an alternative to the current inefficient and artifactual methods of emulsification currently used. With further validation and standardization, lipid vesicle incorporation of petroleum fractions and treatment of cells with these vesicles should be useful for studying the genotoxicity of complex hydrophobic mixtures in cell culture systems.

Health hazards of natural and introduced chemical components of boatbuilding woods

The major components of untreated wood--cellulose, hemicellulose, and lignin--have not been implicated as toxicants, but extractive substances, especially in heartwood, can be toxic. Decay-resistant woods are more likely to contain irritants or sensitizers than nondurable woods. Short-term exposures to certain wood dusts may result in asthma, conjunctivitis, rhinitis, or allergic dermatitis, but long-term effects may include nasal cancer and Hodgkin's disease. Some thermophilic microorganisms found in wood are human pathogens, and septic splinters (chromomycosis) and inhalation of ascomycete spores from stored wood chips have been implicated in human illnesses. Reconstituted wood can contain formaldehyde resins, which pose health risks in enclosed humid areas. Pentachlorophenol (PCP)-treated wood is particularly toxic--short-term exposures to PCP-treating solutions can lead to aplastic anemia and mortality, while diseases such as Hodgkin's disease are associated with long-term exposures. Since much commercial lumber is dipped in PCP, the separation of the chronic effects of wood dust from PCP exposure is difficult. Chromated copper arsenate (CCA)- and ammoniacal copper arsenite (ACA)-treated wood may leach arsenic. CCA-treated wood is potentially safer, since it contains the pentavalent arsenic, which is a common constituent in the environment. ACA contains the trivalent arsenic, which is more toxic.

Cancer and polluted work places: a case-control study

The possible association between selected cancers and polluted work places has been studied in a hospital-based, case-control study. By dividing all jobs in the participants working career into "polluted" and "clean", a crude measure for the total industrial exposure a worker experiences throughout his life was established. Among 103 age-matched, case-control pairs the overall estimated relative risk (RR) for exposed subjects (greater than or equal to 10 years in a polluted work place) of developing cancer compared to nonexposed (less than 10 years in a polluted work place) was 1.1. The only subgroup where a significant difference was found between the cases and the controls was the lung cancer subgroup (RR = 4.0, p = 0.02, two-tailed). When the 30 lung cancer cases were compared to an alternative control group consisting of 60 subjects matched for age and smoking habits, an estimated RR of 4.5 was found. A moderate, but not significant association between lung cancer and definite asbestos exposure was also found (RR: 2.3). As most workers are exposed to a variety of industrial agents throughout their working careers, further development of methods for characterizing combined exposures are needed, both for retrospective and prospective purposes.