Associations between several sites of cancer and twelve petroleum-derived liquids. Results from a case-referent study in Montreal

Interpretation of male rat renal tubule tumors

Based on an analysis of recent scientific studies, a Technical Panel of the U.S. Environmental Protection Agency's (EPA) Risk Assessment Forum recently advised EPA risk assessors against using information on certain male rat renal tubule tumors to assess human risk under conditions specified in a new Forum report. Risk assessment approaches generally assume that chemicals producing tumors in laboratory animals are a potential cancer hazard to humans. For most chemicals, including classical rodent kidney carcinogens such as N-ethyl-N-hydroxyethylnitrosamine, this extrapolation remains appropriate. Some chemicals, however, induce accumulation of alpha 2u-globulin (alpha 2u-g), a low molecular weight protein, in the male rat kidney. The alpha 2u-g accumulation initiates a sequence of events that appears to lead to renal tubule tumor formation. Female rats and other laboratory mammals administered the same chemicals do not accumulate low molecular weight protein in the kidney, and they do not develop renal tubule tumors. Because humans appear to be more like other laboratory animals than like the male rat, in this special situation, the male rat is not a good model for assessing human risk. The Forum report stresses the need for full scrutiny of a substantial set of data to determine when it is reasonable to presume that renal tumors in male rats are linked to a process involving alpha 2u-g accumulation and to select appropriate procedures for estimating human risks under such circumstances.

Kidney cancer and hydrocarbon exposures among petroleum refinery workers

To evaluate the hypothesis of increased kidney cancer risk after exposure to hydrocarbons, especially those present in gasoline, we conducted a case-control study in a cohort of approximately 100,000 male refinery workers from five petroleum companies. A review of 18,323 death certificates identified 102 kidney cancer cases, to each of whom four controls were matched by refinery location and decade of birth. Work histories, containing an average of 15.7 job assignments per subject, were found for 98% of the cases and 94% of the controls. To each job, industrial hygienists assigned semiquantitative ratings for the intensity and frequency of exposures to three hydrocarbon categories: nonaromatic liquid gasoline distillates, aromatic hydrocarbons, and the more volatile hydrocarbons. Ratings of "present" or "absent" were assigned for seven additional exposures: higher boiling hydrocarbons, polynuclear aromatic hydrocarbons, asbestos, chlorinated solvents, ionizing radiation, and lead. Each exposure had either no association or a weak association with kidney cancer. For the hydrocarbon category of principal a priori interest, the nonaromatic liquid gasoline distillates, the estimated relative risk (RR) for any exposure above refinery background was 1.0 (95% confidence interval [CI] 0.5-1.9). Analyses of cumulative exposures and of exposures in varying time periods before kidney cancer occurrence also produced null or near-null results. In an analysis of the longest job held by each subject (average duration 9.2 years or 40% of the refinery work history), three groups appeared to be at increased risk: laborers (RR = 1.9, 95% CI 1.0-3.9); workers in receipt, storage, and movements (RR = 2.5, 95% CI 0.9-6.6); and unit cleaners (RR = 2.3, 95% CI 0.5-9.9).

Mortality of professional chemists in England and Wales, 1965-1989

Several studies on the mortality of chemists have revealed a lower overall mortality but an excess of deaths from certain diseases, in particular, cancers. This study determined the causes of mortality of 4,012 chemists among 14,884 members of The Royal Society of Chemistry who were followed for a period of 25 years. The results demonstrated consistency with other studies. There was an overall low mortality rate, with fewer deaths than expected from cancers, but an excess mortality from lymphatic and hematopoietic cancers, in particular leukemias. There was an excess of deaths from certain gastrointestinal cancers. There was reduced mortality from respiratory diseases, including lung cancers, and from cardiovascular disease. New findings reported in this study are increased mortality from cancers of the duodenum and kidney, certain skin cancers, mental disorders, and diseases of the nervous system.

Issues and controversies surrounding qualitative strategies for identifying and forecasting cancer causing agents in the human environment

Certain chemicals, mixtures of chemicals, exposure circumstances, life-styles and personal or cultural habits, occupations, viruses, living conditions, and physical agents have been causally associated with cancers in humans. Most however are not considered potentially carcinogenic, and the proportion of 'agents' eventually identified to cause cancer is projected to be relatively low. Current methods to identify carcinogenic potential of chemicals rely largely on short-term in vitro and in vivo tests, mid- & long-term in vivo assays, molecular mechanisms, epidemiological investigations, and structural-activity-effect-relationships. Thus, the scientific and public health communities must continue to utilize available means and concomitantly strive to develop newer methods and tools to more easily, quickly, cheaply, and reliably identify carcinogens in the human milieu. Since adequate human studies are typically absent, the most useful method for identifying potential human carcinogens continues to be long-term carcinogenesis experiments. Agents identified as causing cancers in humans have been shown to cause cancer in animals, and this knowledge, together with similarities in mechanisms of carcinogenesis across species, led to the scientific logic and public health strategy that chemicals shown clearly to be carcinogenic in animals should be considered as being likely and anticipated to present cancer risks to humans. The quest of hazard identification efforts is cancer prevention, largely by reducing or eliminating exposures to chemicals that cause cancer and other diseases.

An alternative hypothesis on the role of chemically induced protein droplet (alpha 2u-globulin) nephropathy in renal carcinogenesis

Based on associations between the accumulation of protein droplets containing alpha 2u-globulin in proximal tubular epithelial cells and increased incidences of renal tubular neoplasms in male rats, it has been suggested that the carcinogenicity of chemicals that cause alpha 2u-globulin nephropathy is unique to animals that synthesize this protein. Chemicals that caused alpha 2u-globulin nephropathy and renal carcinogenicity in male rats have not been shown to produce renal tumors in animals that lack the capability for hepatic alpha 2u-globulin synthesis, including female rats, male NBR rats, or mice of either sex. Because humans do not synthesize alpha 2u-globulin it has been suggested that chemicals which cause renal toxicity associated with alpha 2u-globulin accumulation do not pose an increased cancer risk to humans. In this review on the association between alpha 2u-globulin nephropathy and renal carcinogenesis, it is apparent that (a) there are data inconsistent with the hypothesis linking these occurrences, (b) alternative mechanisms of renal toxicity and carcinogenicity are plausible, (c) data on quantitative dose-response correspondences between the various stages of alpha 2u-globulin nephropathy and renal carcinogenicity are limited, and (d) a greater understanding of the molecular changes occurring during renal carcinogenesis is needed before assuming that the current hypothesis is correct. Future research aimed at resolving issues raised in this paper should help determine whether or not the association between alpha 2u-globulin nephropathy and renal carcinogenesis represents a cause-and-effect relationship.

Patterns and risks of cancer in farmers in Alberta

Data on occupations and life styles of patients with cancer have been collected since 1983. To investigate cancer patterns and risks in farmers in Alberta, all farmers were abstracted and compared with nonfarmers in the data base, using case-control analysis. Controls were patients with cancer at any site except the index site. Significantly elevated odds ratio (OR), adjusted for age and smoking, were found among the farmers for cancers of the lip (OR = 3.22, 95% confidence interval [CI] = 2.14 to 4.84) and prostate (OR = 1.31, 95% CI = 1.11 to 1.55). Crude risk for lung cancer was significantly lower in farmers, but statistical significance disappeared when risk was adjusted for smoking (OR = 0.81, 95% CI = 0.65 to 1.02). Farmers were at considerably lower risk of malignant melanoma of the skin, compared with nonfarmers (OR = 0.57, 95% CI = 0.36 to 0.91).

Development, use, and availability of a job exposure matrix based on national occupational hazard survey data

A job exposure matrix has been developed based on potential exposure data collected during the 1972-1974 National Occupational Hazard Survey (NOHS). The survey sample was representative of all U.S. non-agricultural businesses covered under the Occupational Safety and Health Act of 1970 and employing eight or more employees. Potential worker exposure to all chemical, physical, or biological agents was recorded during the field survey if certain minimum guidelines for exposure were met. The job exposure matrix (JEM) itself is a computerized database that assists the user in determining potential chemical or physical exposures in occupational settings. We describe the structure and possible uses of the job exposure matrix. In one example, potential occupational exposures to elemental lead were grouped by industry and occupation. In a second example, the matrix was used to determine exposure classifications in a hypothetical case-control study. Present availability as well as future enhancements of the job exposure matrix are described.

Cancer among captains and mates on Norwegian tankers

A cohort of 1687 registered captains and mates from a Norwegian census in 1970 was followed until 1987 using a historical prospective design. By matching the data from the census to the Norwegian Cancer Registry, 104 cases of cancer were found. A control group of 376 was chosen among non-cases at baseline (1970). Information about the seamen's work on different ships was obtained from the National Register of Norwegian Seamen. The material was analysed using multivariate logistic regression. An increased risk of developing cancer was found in the group of seamen who had been working on tankers, especially oil tankers (OR = 6.47, 95%CI: 1.14, 7.24). The increased risk was found to be significantly correlated to working as mate on these tankers (OR = 6.95, 95%CI: 3.70, 13.04), whereas working as captain showed a much lower risk (OR = 1.42, 95%CI: 0.64, 3.15). Chemical exposure is the major factor separating tankers from other ships. Mates are exposed to chemicals while captains are not. The study indicates the presence of several carcinogenic agents on these tankers.

Occupational cancer mortality in Illinois white and black males, 1979-1984, for seven cancer sites

A death certificate mortality odds ratio study of seven cancer sites was conducted by using 1979-1984 data on Illinois deaths in white and black males. Cancer sites selected include stomach, pancreas, lung, prostate, bladder, brain, and non-Hodgkin's lymphomas. This surveillance study was undertaken to detect occupational associations that might suggest further avenues of research. Some of the occupations and industries found to have elevated cancer risks and that are consistent with previous studies include: brickmasons and stonemasons (stomach); metal workers (pancreas, lung); photoengravers and lithographers (pancreas); butchers (lung); locomotive operators and truck drivers (lung); farmers (prostate, brain, non-Hodgkin's lymphoma); mechanics and repairers, especially auto mechanics (prostate); physicians (brain); glass products manufacturing workers (brain); and communications industry (brain) and chemical plant workers (non-Hodgkin's lymphomas). It was also noted that for black males, the death certificate occupational data are of limited usefulness due to the high percentage of missing or inexact information. The Division of Vital Records in the State of Illinois should make an effort to improve the reporting of this data through additional training of the funeral directors and hospital clerks who collect this information and by follow-up of incomplete or missing data.

Aviation gasoline: comparative subchronic nephrotoxicity study in the male rat

Biochemical and histopathologic parameters of nephrotoxicity were measured in groups of male Fischer-344 rats after a 2-week, 5-days-a-week schedule of oral administration (0.5 ml/kg) of the following substances: aviation gasoline (grade 100) (AVG), automobile regular unleaded gasoline (ULG) and 2,2,4-trimethylpentane (TMP). Results of renal histopathologic examinations and biochemical parameters were compatible with the following order of increasing nephrotoxicity: ULG less than TMP less than AVG. The high nephrotoxic potential of aviation gasoline may be related to its elevated content in branched hydrocarbons.