Multiple myeloma and occupation in Sweden

Multiple myeloma and diesel and other occupational exposures in swedish construction workers

We examined the relationships between occupational exposures and the risk of multiple myeloma among male construction workers in Sweden. A total of 446 myeloma subjects were identified among 365,424 male workers followed from 1971 to 1999. Occupational exposure was assessed using a semiquantitative job-exposure matrix, based on a survey carried out by the Construction Industry's Organization for Working Environment, Occupational Safety and Health in Sweden. Rate ratios (RRs) in the exposed groups relative to the unexposed groups were estimated by Poisson regression. We found an increased risk (RR = 1.3, 95% CI 1.04-1.71) among construction workers exposed to diesel exhaust. Adjustment for other occupational exposures did not change this estimate (RR = 1.3, 95% CI 1.00-1.77). However, there was no monotonic increase in risk with estimated level of exposure (RR for low = 1.4, moderate = 1.1, high = 1.4). There was no evidence of increased risk associated with the other occupational exposures among these construction workers, including asbestos, asphalt, cement dust, metal dust, mineral wool, organic solvents, stone dust and wood dust. Occupational exposure to diesel exhaust in the Swedish construction industry may present a small risk of multiple myeloma, but lack of an exposure-response trend tempers our ability to draw clear conclusions.

Myeloma aetiology and epidemiology

Recently there have been substantial improvements in our understanding of the biology of myeloma. These findings have important implications for aetiological studies aimed at defining the causative factors for myeloma. Myeloma is closely related to monoclonal gammopathy of unknown significance (MGUS), which is now recognized to be very common in the older population. The epidemiology of these conditions is presented and discussed in the context of the genetic factors governing both the risk of developing MGUS or of transformation to myeloma. Biological studies support a role for aberrant class switch recombination early in the natural history of myeloma suggesting that factors in the environment may interact with this mechanism to increase myeloma risk. Case-control and cohort studies have identified several known and suspected environmental exposures. These exposures include high doses of ionizing radiation, and occupational exposure in the farming and petrochemical industries. The data supporting these associations are presented and discussed in the context of the molecular mechanisms underlying these exposures. In particular DNA damage occurring as a consequence could readily interact with the class switch recombination process to increase the risk of chromosomal translocations, oncogene deregulation and malignant transformation. A further hypothesis, which has been extensively investigated, is the role of chronic immune/antigenic stimulation and the risk of myeloma. This concept is difficult to explain in the context of our current immunological concepts. The data supporting the association and how molecular epidemiological studies using genetic variants in cytokine genes are allowing us to revisit this concept are discussed in detail.

Cancer mortality patterns among hairdressers and barbers in 24 US states, 1984 to 1995

We evaluated cancer mortality patterns among hairdressers and barbers, according to occupation, coded on 7.2 million death certificates in 24 states from 1984 to 1995. Of the 38,721 deaths among white and black hairdressers and barbers of both sexes, 9495 were from all malignant neoplasms. Mortality odds ratios were significantly elevated for all malignant neoplasms, lung cancer, and all lymphatic and hemopoietic cancers among black and white female hairdressers. White female hairdressers had significant excess mortality from cancers of the stomach, colon, pancreas, breast, and bladder and from non-Hodgkin's lymphoma and lymphoid leukemia; mortality from these cancers was also elevated among black female hairdressers. White male hairdressers had significantly elevated mortality from non-melanoma skin cancer and non-Hodgkin's lymphoma. Mortality from all malignant neoplasms, although significantly elevated among both white and black female hairdressers, was significantly below the null for white male hairdressers. Black and white male barbers had significantly elevated mortality from stomach and pharyngeal cancer, respectively. A significant deficit in mortality from all neoplasms and cancers of the pancreas, lung, and prostate was noted for white male barbers. This large study of cancer mortality among hairdressers and barbers showed some differences in mortality patterns by gender and race. Further studies are required to determine if specific occupational exposures may explain some of the elevated cancer rates.

Racial differences in the prevalence of monoclonal gammopathy in a community-based sample of the elderly

PURPOSE

To determine if there is an increased prevalence of monoclonal gammopathy in elderly blacks compared with whites, analogous to the difference in incidence of multiple myeloma reported for the two racial groups and to confirm age and gender relationships.

PATIENTS AND METHODS

Subjects were from the Duke Established Populations for the Epidemiologic Study of the Elderly, selected on the basis of stratified random household sampling. Blacks were oversampled to allow for increased statistical precision in racial comparisons. In all, 1,732 subjects (aged > 70 years) consented to blood drawing and constitute the sample for this study. Monoclonal immunoglobulins were determined by agarose gel electrophoresis and immunofixation.

RESULTS

One hundred six subjects (6.1%) had a monoclonal gammopathy. There was a greater than twofold difference in prevalence between blacks (8.4%) and whites (3.8%) (P < 0.001); monoclonal gammopathy prevalence increased with age, and was greater in men than women. Those with monoclonal gammopathy did not differ from those without in socioeconomic status, urban/rural residence, or education. The presence of monoclonal gammopathy was not associated with any specific diseases nor with impaired functional status. There was a slight increase in serum creatinine levels and decrease in hemoglobin and albumin levels in patients with monoclonal gammopathy, but no difference in interleukin-6 (IL-6) levels. Moreover, IL-6 levels were not correlated significantly with the level of monoclonal protein.

CONCLUSION

Prevalence of monoclonal gammopathy is significantly greater among blacks than whites in a community-based sample, in approximately the same ratio that multiple myeloma has been reported in the two groups. Given the absence of correlation with environmental factors, there may be a biological racial difference in susceptibility to an early event in the carcinogenic process leading to multiple myeloma.

Hematopoietic and lymphatic malignancies in vehicle mechanics

Although it is generally acknowledged that benzene causes leukemia, especially acute myeloid leukemia, considerable divergences persist in the assessment of the leukemia risk due to occupational low-level benzene exposure. Specifically, the risk for vehicle mechanics is considered by some authors as being nondetectable with epidemiologic methods, whereas others calculated that the incidence rate of leukemia (all types) in vehicle mechanics is increased more than 60 times. The purpose of this review is to examine the publications on this topic in light of criteria for causal inference and to discuss the possible role of bias, confounding factors, and chance. The results of this analysis reveal that there are surprisingly few epidemiologic observations supporting an increased incidence of leukemia in vehicle mechanics. Apparently, publications suggesting a leukemogenic effect of low-level benzene exposure in garage mechanics are more often quoted than their negative counterparts, although they are not better designed.

Lymphoma, myeloma and occupation: results of a case-control study

The known risk factors for lymphoma and myeloma cannot account for the current incidence rates of these cancers, and there is increasing interest in exploring occupational causes. We present results regarding lymphoma and myeloma from a large case-control study of hundreds of occupational exposures and 19 cancer sites. We examine in more detail those exposures previously considered to be related to these cancers, as well as exposures which were strongly related in our initial analyses. Lymphoma was not associated in our data with exposure to solvents or pesticides, or employment in agriculture or wood-related occupations, although numbers of exposed cases were sometimes small. Hodgkin's lymphoma was associated with exposure to fabric dust, and non-Hodgkin's lymphoma was associated with exposure to copper dust, ammonia and a number of fabric and textile-related occupations and exposures. Employment as a sheet metal worker was associated with development of myeloma.

Lymphoma, multiple myeloma and leukaemia among French farmers in relation to pesticide exposure

Lymphoma, multiple myeloma and leukaemia mortality among French male farmers and farm laborers (1984-1986) has been studied geographically. In each geographical area (89 "départements") exposure to pesticides in arable land has been characterized by an index taking into account different practices in the treatment of various crops as well as an estimate of the time per farmer spent cultivating each crop in 1970. The farmers population as a whole presented an increased mortality for multiple myeloma (SMR = 1.59, 95% CI = 1.32-1.89) and leukaemia (SMR = 1.33, 95% CI = 1.19-1.49) but not for lymphoma (SMR = 1.09, 95%, CI = 0.94-1.26). Using Poisson regression, leukaemia mortality appeared significantly linked to the pesticide exposure index (P = 0.04), after adjustment of farmers' economic status and a linear geographical gradient, whereas no significant relationship was found for lymphoma or multiple myeloma. This result reinforces a similar link reported from a previous French geographical study conducted at a smaller scale within a region.

Occupational risk factors for multiple myeloma among Danish men

A large population-based case-control study evaluated occupational exposures in 1,098 Danish males diagnosed with multiple myeloma from 1970 to 1984 and in 4,169 age- and gender-matched controls alive at the time of case-diagnosis. Industrial histories were obtained from the Supplementary Pension Fund which, since 1964, has recorded employments of adult Danes; occupation came from subjects' most recent tax records. Four industrial hygienists created a job-exposure matrix for 47 substances based on 15,000 unique industry/occupation combinations in subjects' histories. Risk of myeloma was significantly elevated among road and railroad workers, precision metalworkers, and workers in the transportation and communication industries. Risk increased significantly with duration of employment in: production of synthetic yarns, plastic packaging, and miscellaneous chemical compounds; fabricating structural metal and stationary tanks; body factories; electrical plants; and retail sale of paint and wallpaper. Risks of myeloma were elevated, though statistically nonsignificantly, in all categories of exposure to gasoline and engine exhausts. Risks rose with likelihood and duration of exposure to phthalates, and were statistically significant and nearly fivefold with probable exposure to vinyl chloride for five or more years. After adjusting for multiple exposures and disregarding exposures within 10 years of diagnosis (or selection as a control), probable exposure to vinyl chloride was associated with increased risk of myeloma, which rose to fivefold with longer exposure. Associations with gasoline, engine exhausts, and phthalates persisted, but were inconsistent with duration and probability of exposure. Previously reported associations with agriculture were not confirmed by these data.

Multiple myeloma among Danish women: employment history and workplace exposures

To investigate the role of employment history and workplace exposures as risk factors for multiple myeloma among women, a population-based case-control study using the Danish Cancer Registry data linkage system was conducted. All cases of myeloma diagnosed in Danish women between 1970 and 1984 (1,010 cases) and 4,040 age-matched women alive at the time of case-diagnosis were identified. Industrial histories from 1964 forward were obtained from the nationwide Pension Fund for 363 cases and 1,517 controls, and the most recent occupation on the tax record was available for 607 cases and 2,596 controls. Using industry/occupational-code combinations for the cases and controls who had industry employment, Danish industrial hygienists assessed the likelihood of exposure to 47 workplace substances. An increased myeloma risk (odds ratio [OR] = 1.2, 95 percent confidence interval [CI] = 1.0-1.5) was seen for women not in the Pension Fund, but who had an occupational title coded as 'Mrs/homemaker.' Nonsignificantly elevated risks of 1.3 or greater were observed for employment in: production of agricultural products; orchards/nurseries; spinning/weaving; other textile and plastics manufacturing; hotel, entertainment, and social services industries. Elevated, but nonsignificant risks were observed for possible and probable exposure to exhaust fumes, formaldehyde, wood dust, animals or animal products, and pesticides. The strongest association with myeloma was employment in the agricultural industry (OR = 1.5, CI = 0.8-2.8), however, the number of women who worked on family farms was unknown and could not be included in this risk estimate.

Occupational and other environmental factors and multiple myeloma: a population based case-control study

Epidemiological studies on the aetiology of multiple myeloma are reviewed as a background to this population based case-control study performed in an area with a high incidence of multiple myeloma. The purpose was to identify and evaluate several suspected environmental factors in relation to this disease. A total of 275 confirmed cases diagnosed in four counties in northern Sweden during four years were compared with the same number of control subjects drawn from population registries. The controls were matched for age, sex, county, and vital status. Occupations and work associated exposures to chemicals and other potential carcinogens were assessed by an extensive questionnaire that also included questions on smoking habits, residential building materials, vicinity to electrical power lines, and leisure time contact with animals, electrical equipment, and chemicals. Information obtained from the questionnaires was completed by telephone interviews when necessary. Univariate analysis and multivariate logistic regression were performed. The study confirmed an association found earlier between farming and multiple myeloma. Some domestic animals (cattle, horses, and goats) and two types of pesticides (phenoxyacetic acids and DDT) were indicated as risk factors within farming. Exposure to electromagnetic fields, asbestos, and organic solvents were negatively associated with myeloma in this study.

A cohort study on cancer incidence among Danish gardeners

This study was performed to examine the cancer risk of Danish gardeners having been highly exposed to pesticides. We have followed a cohort of 4,015 employed gardeners (859 females and 3,156 males) from May 1975 until the end of 1984 with regard to cancer incidence. The observed incidence was compared with expected numbers calculated from national incidence rates. For all cancer sites combined, the standardized morbidity ratio (SMbR) was 104. Among male gardeners a significantly increased incidence was seen for soft tissue sarcoma (SMbR = 526, 95% confidence interval (CI): 109-1,538), an chronic lymphatic leukemia (SMbR = 275, 95% CI: 101-599). The incidence of non-Hodgkin's lymphoma was twice that which was expected (SMbR = 200, 95% CI: 86-393). We suggest that some of the pesticides to which the gardeners have been exposed are capable of initiating or promoting the development of malignant neoplasms in tissues of mesenchymal origin.

Malignant lymphoproliferative diseases in occupations with potential exposure to phenoxyacetic acids or dioxins: a register-based study

The Swedish Cancer Environment Register (CER) is a linkage of census data (e.g., on occupations) with the Swedish Cancer Register. It has been used in different studies to generate hypotheses on occupational risk factors for malignant tumors. In this study the risk for malignant lymphoma and multiple myeloma in occupations with potential exposure to phenoxyacetic acids or other related substances were investigated. An increased standardized incidence ratio (SIR) of 1.3 for multiple myeloma was verified in farmers (no. of cases = 335). This finding applied to both sexes, and the SIR increased over successive time periods. Regarding malignant lymphoma an increased SIR of 1.2 was found in farmers (no. = 227) for the latest time period studied (i.e. 1979-1984). When non-Hodgkin's lymphoma was studied separately, an increased risk (SIR = 1.2) was found only in carpenters (no. = 149), whereas for Hodgkin's disease, sawmill workers (no. = 10) had an increased SIR of 2.1. Physicians also had an elevated risk for malignant lymphoma. A major shortcoming in register studies such as CER is that no individual exposure data on different agents are available. Lack of an association between an occupation and a specific malignant disease, therefore, may not be taken as evidence that persons within that occupation are not at increased risk for that disease.

A case-control study of multiple myeloma nested in the American Cancer Society prospective study

Among the subjects enrolled in the American Cancer Society Cancer Prevention Study II, a large nation-wide prospective study, 282 died from multiple myeloma (MM) during the first 4 years of follow-up. These were divided into incident cases who were initially free from disease and prevalent cases who reported MM or related symptoms at the time of enrollment. For each case, 4 controls matched for age, sex, ethnic group and residence were randomly selected. Previous history of diabetes [odds ratio (OR) = 2.0] and employment as farmer (OR = 2.7) were the risk factors consistently suggested by the results of the analysis. The risk associated with farming showed a linear trend with duration of exposure. Pesticide or herbicide exposure was not a risk factor per se but, when combined with farming, it increased the OR to 4.3. Low education, occupational exposure to dyes, and employment in a bank, on the railroad or as a maid were also suggested risk factors, but either they were not statistically significant or they were based on small numbers of exposed subjects. No association between MM and asbestos exposure was observed.