Multiple myeloma and engine exhausts, fresh wood, and creosote: a case-referent study

Diesel Exhaust Exposure and Cause-Specific Mortality in the Diesel Exhaust in Miners Study II (DEMS II) Cohort

BACKGROUND

With the exception of lung cancer, the health effects associated with diesel exhaust for other cancers and nonmalignant health outcomes are not well understood.

OBJECTIVES

We extended the mortality follow-up of the Diesel Exhaust in Miners Study, a cohort study of 12,315 workers, by 18 y (ending 31 December 2015), more than doubling the number of observed deaths to n = 4,887 , to evaluate associations between mortality and diesel exhaust exposure.

METHODS

Quantitative estimates of historical exposure to respirable elemental carbon (REC), a surrogate for diesel exhaust, were created for all jobs, by year and facility, using measurements collected from each mine, as well as historical measurements. Standardized mortality ratios (SMRs) and hazard ratios (HRs) were estimated for the entire cohort and by worker location (surface, underground).

RESULTS

We observed an excess of death for cancers of the lung, trachea, and bronchus (n = 409 ; SMR = 1.24 ; 95% CI: 1.13, 1.37). Among workers who ever worked underground, where the majority of diesel exposure occurred, excess deaths were evident for lung, trachea, and bronchus cancers (n = 266 ; SMR = 1.26 ; 95% CI: 1.11, 1.42). Several nonmalignant diseases were associated with excess mortality among workers ever-employed underground, including ischemic heart disease (SMR = 1.08 ; 95% CI: 1.00, 1.16), cerebrovascular disease (SMR = 1.22 ; 95% CI: 1.04, 1.43), and nonmalignant diseases of the respiratory system (SMR = 1.13 ; 95% CI: 1.01, 1.26). Continuous 15-y lagged cumulative REC exposure < 1,280   μ g / m 3 -y was associated with increased lung cancer risk (HR = 1.93 ; 95% CI: 1.24, 3.03), but the risk declined at the highest exposures (HR = 1.29 ; 95% CI: 0.74, 2.26). We also observed a significant trend in non-Hodgkin lymphoma (NHL) risk with increasing 20-y lagged cumulative REC (HR Tertile 3  vs. Tertile 1 = 3.12 ; 95% CI: 1.00, 9.79; p -trend = 0.031 ).

DISCUSSION

Increased risks of lung cancer mortality observed in the original study were sustained. Observed associations between diesel exposure and risk of death from NHL and the excesses in deaths for diseases of the respiratory and cardiovascular system, including ischemic heart disease and cerebrovascular disease, warrant further study and provide evidence of the potential widespread public health impact of diesel exposure. https://doi.org/10.1289/EHP12840.

Occupational Exposure and Multiple Myeloma Risk: An Updated Review of Meta-Analyses

The precise etiology of multiple myeloma remains elusive, but both genetic and environmental factors have been suggested to contribute to disease risk. Several occupational categories and toxic agents have been implicated as potentially causative, yet findings from the literature are inconsistent. The aim of this review was to summarize and critically comment on the accumulated epidemiological evidence, across published meta-analyses, about the association between occupational exposure and risk of multiple myeloma. Overall, results from eleven meta-epidemiological studies underscore a significantly increased risk for firefighters, hairdressers, and employees exposed to engine exhaust, whereas farming and methylene chloride exposure have been non-significantly correlated with the disease. Further epidemiological studies are of utmost importance whilst emphasis should be placed on occupational hazard surveillance, as such studies will obtain a more accurate picture of disease occurrence in working populations, and will enable both the implementation of preventive actions and the evaluation of their effectiveness.

Risk of multiple myeloma in a case-spouse study

This study examined lifestyle, occupation, medical history and medication use with multiple myeloma risk in a case-spouse study (481 patients, 351 spouses). Odds ratios (ORs) and 95% confidence intervals (CI) were calculated using logistic regression. Compared to spouse controls, cases were more likely to have a family history of multiple myeloma (OR = 2.8, 95% CI = 1.2-6.4) and smoked cigarettes (OR = 1.7, 95% CI = 1.2-2.5), but less likely to have consumed alcohol (OR = 0.6, 95% CI = 0.4-0.9). Nurse/health practitioners (OR = 2.8, 95% CI = 1.3-6.2) and production workers (OR = 3.7, 95% CI = 1.0-13.7) had significantly increased risks; and some occupations linked to diesel exhaust had elevated, but non-significant, risks. History of herpes simplex (OR = 1.7, 95% CI = 1.2-2.4), shingles (OR = 1.7, 95% CI = 1.1-2.7), sexually transmitted diseases (OR = 2.0, 95% CI = 1.0-3.7) and medication allergies (OR = 1.7, 95% CI = 1.2-2.4) were associated with higher risks. Use of angiotensin-converting enzyme inhibitors, anti-convulsants, antidepressants, statins and diuretics were associated with reduced risks. The results are consistent with previous population-based studies and support the utility of patient databanks and spouse controls as a resource in epidemiologic research.

An evidence-based analysis of epidemiologic associations between lymphatic and hematopoietic cancers and occupational exposure to gasoline

The presence of benzene in motor gasoline has been a health concern for potential increased risk of acute myelogenous leukemia and perhaps other lymphatic/hematopoietic cancers for approximately 40 years. Because of the widespread and increasing use of gasoline by consumers and the high exposure potential of occupational cohorts, a thorough understanding of this issue is important. The current study utilizes an evidence-based approach to examine whether or not the available epidemiologic studies demonstrate a strong and consistent association between occupational exposure to gasoline and lymphatic/hematopoietic cancers. Among 67 epidemiologic studies initially identified, 54 were ranked according to specific criteria relating to the relevance and robustness of each study for answering the research question. The 30 highest-ranked studies were sorted into three tiers of evidence and were analyzed for strength, specificity, consistency, temporality, dose-response trends and coherence. Meta statistics were also calculated for each general and specific lymphatic/hematopoietic cancer category with adequate data. The evidence-based analysis did not confirm any strong and consistent association between occupational exposure to gasoline and lymphatic/hematopoietic cancers based on the epidemiologic studies available to date. These epidemiologic findings, combined with the evidence showing relatively low occupational benzene vapor exposures associated with gasoline formulations during the last three decades, suggest that current motor gasoline formulations are not associated with increased lymphatic/hematopoietic cancer risks related to benzene.

Disease risk score as a confounder summary method: systematic review and recommendations

PURPOSE

To systematically examine trends and applications of the disease risk score (DRS) as a confounder summary method.

METHODS

We completed a systematic search of MEDLINE and Web of Science® to identify all English language articles that applied DRS methods. We tabulated the number of publications by year and type (empirical application, methodological contribution, or review paper) and summarized methods used in empirical applications overall and by publication year (<2000, ≥2000).

RESULTS

Of 714 unique articles identified, 97 examined DRS methods and 86 were empirical applications. We observed a bimodal distribution in the number of publications over time, with a peak 1979-1980, and resurgence since 2000. The majority of applications with methodological detail derived DRS using logistic regression (47%), used DRS as a categorical variable in regression (93%), and applied DRS in a non-experimental cohort (47%) or case-control (42%) study. Few studies examined effect modification by outcome risk (23%).

CONCLUSION

Use of DRS methods has increased yet remains low. Comparative effectiveness research may benefit from more DRS applications, particularly to examine effect modification by outcome risk. Standardized terminology may facilitate identification, application, and comprehension of DRS methods. More research is needed to support the application of DRS methods, particularly in case-control studies.

Occupation and multiple myeloma: an occupation and industry analysis

BACKGROUND

Multiple myeloma (MM) is an incurable plasma cell malignancy with a poorly understood etiology. The purpose of our research was to examine the relationships between lifetime occupations and MM in a relatively large case-control study.

METHODS

MM cases (n = 180) were identified through cancer registries in the Seattle-Puget Sound area and Detroit. Population-based controls (n = 481) were identified using random digit dialing and Medicare and Medicaid Services files. In-person interviews were conducted to ascertain occupational histories. Standard occupational classification (SOC) and standard industrial classification (SIC) codes were assigned to each job held by each participant. Unconditional logistic regression was used to generate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between MM and having ever worked in each occupation/industry and according to duration of employment in an occupation/industry.

RESULTS

The risk of MM was associated with several manufacturing occupations and industries, including machine operators and tenders, not elsewhere classified (SOC 76) (OR = 1.8, CI = 1.0-3.3); textile, apparel, and furnishing machine operators and tenders (SOC 765) (OR = 6.0, CI = 1.7-21); and machinery manufacturing, except electrical (SIC 35) (OR = 3.3, CI = 1.7-6.7). Several service occupations and industries, such as food and beverage preparation (SOC 521) (OR = 2.0, CI = 1.1-3.8), were also associated with MM. One occupation that has been associated with MM in several previous studies, painters, paperhangers, and plasterers (SOC 644) was associated with a non-significantly elevated risk (OR = 3.6, CI = 0.7-19).

CONCLUSIONS

We found associations between the risk of MM and employment in several manufacturing and service-related occupations and industries.

Multiple myeloma and farming. A systematic review of 30 years of research. Where next?

Background

Multiple myeloma has been linked to farming for over thirty years. However, there is little clarity about the magnitude of the risk, nor about the specific agricultural exposures which contribute to the risk.

Methods

We have carried out a systematic review of case-control studies of multiple myeloma published from 1970 to October 2007. Studies were identified through database searches and from references in the literature.

Studies reporting risk estimates from farming, agricultural exposures, and exposure to animals were identified, and details abstracted. The impact of study heterogeneity, publication bias, variation in methods of case identification and exposure ascertainment between studies were considered in analysis.

Results

Case control studies showed a pooled odds ratio (OR) for working as a farmer of 1.39 95% CI 1.18 to 1.65. There was no graphic evidence of publication bias, for pesticide exposure 1.47; 95% 1.11 to 1.94, for DDT 2.19; CI 95% 1.30 to 2.95; for exposed to herbicides 1.69; 95 %CI 1.01 to 1.83. For working on a farm for more than ten years OR was 1.87; 95% CI 1.15 to 3.16.

Conclusion

Farmers seem to have increase risk for MM. However, a major limitation of this analysis is the presence of significant heterogeneity across the studies and the evidence of publication bias in some models.

A pooled analysis using individual level data could provide more power and permit the harmonization of occupational and exposure coding data.

Risk of leukemia and multiple myeloma associated with exposure to benzene and other organic solvents: evidence from the Italian Multicenter Case-control study

BACKGROUND

While there is a general consensus about the ability of benzene to induce acute myeloid leukemia (AML), its effects on chronic lymphoid leukemia and multiple myeloma (MM) are still under debate. We conducted a population-based case-control study to evaluate the association between exposure to organic solvents and risk of myeloid and lymphoid leukemia and MM.

METHODS

Five hundred eighty-six cases of leukemia (and 1,278 population controls), 263 cases of MM (and 1,100 population controls) were collected. Experts assessed exposure at individual level to a range of chemicals.

RESULTS

We found no association between exposure to any solvent and AML. There were elevated point estimates for the associations between medium/high benzene exposure and chronic lymphatic leukemia (OR = 1.8, 95% CI = 0.9-3.9) and MM (OR = 1.9, 95% CI = 0.9-3.9). Risks of chronic lymphatic leukemia were somewhat elevated, albeit with wide confidence intervals, from medium/high exposure to xylene and toluene as well.

CONCLUSIONS

We did not confirm the known association between benzene and AML, though this is likely explained by the strict regulation of benzene in Italy nearly three decades prior to study initiation. Our results support the association between benzene, xylene, and toluene and chronic lymphatic leukemia and between benzene and MM with longer latencies than have been observed for AML in other studies.

Epidemiology of the plasma-cell disorders

This review of the plasma-cell disorders begins with the definition of monoclonal gammopathy of undetermined significance (MGUS). The prevalence of MGUS in white and black populations is described. MGUS is a common finding in the medical practice of all physicians, and thus it is important to both the patient and the physician to determine whether the monoclonal protein remains stable or progresses to multiple myeloma (MM), Waldenström's macroglobulinemia (WM), primary systemic amyloidosis (AL), or a related disorder. The long-term (almost 40 years) follow-up data of 241 patients in the Mayo Clinic population is provided. In a large study of 1384 patients with MGUS from southeastern Minnesota, the risk of progression to MM, WM, AL, or other disorders was approximately 1% per year. Risk factors for progression are provided. The incidence of MM in Olmsted County, Minnesota, remained stable for the 56-year span 1945-2001. The apparent increase in incidence and mortality rates among patients with MM in many studies is due to improved case ascertainment, especially among the elderly. The incidence and mortality rates of MM in the United States and other countries are presented. The major emphasis is on the cause of MM, which is unclear. Exposure to radiation from atomic bombs, therapeutic and diagnostic radiation, and in workers in the nuclear industry field are addressed. Many studies involving agricultural occupations, exposure to benzene, petroleum products, and engine exhaust and other industrial exposures are discussed. Tobacco use, obesity, diet, and alcohol ingestion are all possible causes of MM. Clusters of MM have been noted. Multiple cases of MM have been found in first-degree relatives.

Multiple myeloma: A review of the epidemiologic literature

Multiple myeloma, a neoplasm of plasma cells, accounts for approximately approximately 15% of lymphatohematopoietic cancers (LHC) and 2% of all cancers in the US. Incidence rates increase with age, particularly after age 40, and are higher in men, particularly African American men. The etiology is unknown with no established lifestyle, occupational or environmental risk factors. Although several factors have been implicated as potentially etiologic, findings are inconsistent. We reviewed epidemiologic studies that evaluated lifestyle, dietary, occupational and environmental factors; immune function, family history and genetic factors; and the hypothesized precursor, monoclonal gammopathies of undetermined significance (MGUS). Because multiple myeloma is an uncommon disease, etiologic assessments can be difficult because of small numbers of cases in occupational cohort studies, and few subjects reporting exposure to specific agents in case-control studies. Elevated risks have been reported consistently among persons with a positive family history of LHC. A few studies have reported a relationship between obesity and multiple myeloma, and this may be a promising area of research. Factors underlying higher incidence rates of multiple myeloma in African Americans are not understood. The progression from MGUS to multiple myeloma has been reported in several studies; however, there are no established risk factors for MGUS. To improve our understanding of the causes of multiple myeloma, future research efforts should seek the causes of MGUS. More research is also needed on the genetic factors of multiple myeloma, given the strong familial clustering of the disease.

Tobacco and alcohol consumption and risk of lymphoma: Results of apopulation-based case-control study in Germany

Changing trends in lifestyle exposures are suggested to be contributing factors to the increasing incidence rates for lymphoma. We investigated the relationship between smoking and alcohol consumption and the risk of lymphoma among adult participants of a population-based case-control study recently conducted in Germany. In 710 case-control pairs, an increased risk of lymphoma was associated with a long duration of smoking (p for trend = 0.01 for men) and smoking of > 20 cigarettes per day(OR = 2.7; 95% CI = 1.4-5.2 for women). Elevated odds ratios were seen for most lymphoma subentities, albeit mostly without reaching statistical significance. A strong association was evident between smoking and multiple myeloma (OR = 2.4, 95% CI = 0.98-5.74 for men; OR = 2.9, 95% CI = 1.1-7.4 for women) and Hodgkin's lymphoma among men (OR = 3.6; 95% CI = 1.7-7.5). Alcohol consumption 10 years prior to the date of interview appeared to decrease the risk of lymphoma. Odds ratios for men who reported alcohol consumption were 53% lower (95% CI = 0.31-0.71) compared to men who drank very little or no alcohol. The same tendency was evident for women, although the association was less pronounced. The inverse relationship was also seen for low amounts of alcohol and did not appear to be restricted to specific types of beverages. Although biologic rationale for a protective effect of alcohol consumption may be given, a more in-depth analysis involving genetic markers is indicated to clarify if ethanol, other components in alcoholic beverages, or factors associated with moderate drinking reduce lymphoma risk among adults. In conclusion, this investigation suggests a positive association between tobacco smoking and lymphoma risk and finds decreased odds ratios among consumers of alcohol.

Retrospective Cohort Mortality Study and Nested Case???Control Study of Workers Exposed to Creosote at 11 Wood-Treating Plants in the United States

OBJECTIVE

The objective of this study was to assess both malignant and nonmalignant mortality risks of workers exposed to creosote. For background, a literature review is also presented.

MATERIALS AND METHODS

The retrospective cohort study consisted of 2179 employees at 11 plants in the United States where wood (primarily railroad ties and utility poles) is treated with creosote-based preservatives. The observation period covered 1979-2001. Mortality data in the cohort study were analyzed in terms of cause-specific standardized mortality ratios (SMRs) and 95% confidence intervals (95% CIs), with expected deaths based on U.S. national cause-, gender-, race-, year-, age-specific mortality rates. In addition to the cohort investigation, a nested case-control study of lung cancer and multiple myeloma was conducted. Information on tobacco consumption and detailed employment (job titles) was obtained for cases and matched controls. Jobs were classified into 5 categories according to potential for exposure to creosote. Odds ratios (ORs) and 95% CIs were calculated for job categories and length of exposure.

RESULTS

Overall mortality for the entire cohort was lower than expected (293 observed deaths vs. 325.37 expected, SMR = 90.1, 95% CI = 80.0-101.0). Close to 90% employees were hourly, whose potential for exposure was generally much higher than that of salaried employees. Among hourly employees, except for multiple myeloma, none of the specific cancer sites showed any significant increase. Furthermore, detailed analysis by length of employment did not reveal any significant mortality excess or upward trend. Six deaths were from multiple myeloma, whereas 1.50 deaths were expected (SMR = 401.1, 95% CI = 147.2-873.1). However, analysis by length of employment did not show any upward trend for multiple myeloma. No significant mortality increase was reported for any nonmalignant disease, and analysis by length of employment did not reveal any upward trend. In the case-control study, an increased risk of lung cancer was associated with tobacco consumption (OR = 4.92) but not with any job/exposure category. For example, the lung cancer odds ratio for routine exposure to creosote-based wood preservatives was 0.58 (95% CI = 0.11-3.03). Similarly, case-control analyses of multiple myeloma did not reveal any association with employment at the plants or with exposure to creosote-based wood preservatives or to creosote-treated products.

CONCLUSION

Based on the present investigation and other studies, there was no evidence that employment at the 11 wood-treating plants or exposure to creosote-based wood preservatives was associated with any significant mortality increase from site-specific cancers or nonmalignant diseases. Some results should be interpreted with caution because they were based on small numbers.

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.

Is There a Causal Relationship Between Exposure to Diesel Exhaust and Multiple Myeloma?

This article presents a comprehensive critical review of the epidemiology of multiple myeloma in relation to occupational diesel exhaust exposure. The review includes cohort and proportional mortality studies of workers exposed to diesel exhaust, and population-based case-control studies of multiple myeloma. None of the cohort or proportional mortality studies reported a significant increase of multiple myeloma in relation to diesel exhaust, with the exception of a study of Danish truck drivers. Several limitations in this Danish study (such as inadequate cohort identification, small number of multiple myeloma deaths and inappropriate analytical method) made the result unreliable. Furthermore, the data in this study of Danish truck drivers were part of and, hence, superseded by a large study in Denmark, which did not find any increased risk of multiple myeloma. Similarly, none of the case-control studies reported a significant increase of multiple myeloma in relation to diesel exhaust, with the exception of the smallest case-control study based on multiple myeloma patients in central and southeast Sweden. The result of this small Swedish study was not reliable because of incomplete case ascertainment, inappropriate controls and confounding. Furthermore, the data in this small Swedish study were part of and, hence, superseded by a large national study of workers exposed to diesel exhaust in Sweden, which did not find any increased risk of multiple myeloma. Other than the study of Danish truck drivers and the small case-control study of multiple myeloma patients in central and southeast Sweden, all other epidemiological investigations consistently reported no increase of multiple myeloma in relation to occupational diesel exhaust exposure. Furthermore, none of the studies reported a positive exposure-response relationship between diesel exhaust and multiple myeloma. Several studies that analysed data by jobs or occupations according to level of exposure and by duration of exposure did not find any upward trend. In addition to the review, a formal causation analysis based on an application of the Hill criteria confirms that there is no causal relationship between diesel exhaust and multiple myeloma.

Significance of radiation exposure from work-related chest X-rays for epidemiological studies of radiation workers

BACKGROUND

Previous epidemiologic studies of workers at nuclear weapons facilities have not included X-ray exposures as part of the occupational radiation exposure. The research objective was to determine the contribution of work-related chest X-ray (WRX) exposure relative to the cumulative occupational radiation exposure.

METHODS

Cases and controls were identified from a cohort of workers whose employment began as early as 1943. Medical records for 297 subjects were used to determine the bone marrow dose from their X-ray examinations. Individual dose data, however, were only available for 45 workers. Bone marrow dose estimates were calculated by converting the entrance-skin-exposure (from X-ray procedures) and occupational exposure (from monitoring data) to dose.

RESULTS

Stereoscopic photofluorography delivered a bone marrow dose nearly 100 times that delivered by today's chest X-ray technique. Photofluorography was the predominant radiation source during the 1940s and 1950s. The cumulative WRX dose was, on average, 50 times their occupational doses. No correlation between occupational and WRX dose was found, but may be due to the small study size and incomplete dose data.

CONCLUSIONS

These findings illustrate the importance of including WRX doses in retrospective epidemiological studies of radiation workers, especially if photofluorographic chest X-rays were performed and occupational exposure to ionizing radiation is low.

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.

Nested case-control study of leukaemia, multiple myeloma, and kidney cancer in a cohort of petroleum workers exposed to gasoline

OBJECTIVES

This nested case-control study was based on data in a cohort study of more than 18,000 petroleum distribution workers exposed to gasoline, which contains about 2%-3% benzene. Risks of leukaemia, acute myeloid leukaemia, multiple myeloma, and kidney cancer were examined relative to exposure to gasoline.

METHODS

For each case, up to five individually matched controls were selected. Analyses based on the Mantel-Haenszel procedure as well as univariate and multivariate conditional logistic regression were performed for each disease category. Jobs with similar exposures were grouped into homogeneous categories for analysis. Several quantitative indices of exposure to gasoline were used in the analyses: duration of exposure, cumulative exposure, frequency of peak exposure, and time of first exposure.

RESULTS

No increased risks for the four cancers were found for any job category. Analyses with logistic regression models based on duration of exposure, cumulative exposure, and frequency of peak exposure did not show any increased risk or exposure-effect relation. Time of first exposure to gasoline was also found to be unrelated to the four diseases under investigation.

CONCLUSION

Exposure to gasoline or benzene at the concentrations experienced by this cohort of distribution workers is not a risk factor for leukaemia (all cell types), acute myeloid leukaemia, multiple myeloma, or kidney cancer.

A case-control study of fatty liver disease and organic solvent exposure

BACKGROUND

Clinical experience of cases of fatty liver disease (FLD) with exposure to organic solvents suggested a possible risk.

METHODS

Thirty male cases of FLD, ages 20-59 years, with biopsy records at departments of pathology in southeast Sweden were compared to 120 male controls randomly drawn from the study area population. Questionnaire information was obtained about job titles and specific occupational exposures; exposure level categories were then assessed blindly for both cases and controls. Medical records for cases were scrutinized to elucidate possible confounding and/or interacting effects from alcohol, the use of drugs, and other diseases.

RESULTS

Moderately intense and mixed solvent exposure for more than 1 year within the last 15 years prior to diagnosis resulted in an age-adjusted Mantel-Haenszel odds ratio of 4.3 (95% confidence interval (CI), 1.2-15); for intense exposure, the odds ratio was 7.7 (95% CI 1.7-48). Confounding from alcohol, use of drugs, other diseases, and overweight could be ruled out with reasonable confidence.

CONCLUSIONS

This study indicates that occupational exposure to organic solvents may play a role in the development of FLD, as indicated earlier in case reports and in one small case-control study.

Multiple myeloma and benzene exposure in a multinational cohort of more than 250,000 petroleum workers

Case reports have suggested an association between benzene exposure and multiple myeloma. Because petroleum workers are exposed to benzene or benzene-containing liquids, studies of these workers provide an opportunity for investigating the relationship between benzene and multiple myeloma. A large number of cohort studies of petroleum workers have been conducted. However, few of them have reported results of multiple myeloma separately. One reason is that multiple myeloma is usually grouped with other lymphopoietic cancers in the analysis. Another reason is that multiple myeloma is relatively rare, and few individual studies are large enough to provide reliable risk estimates. To determine the risk of multiple myeloma in petroleum (refinery, distribution, production, and pipeline) workers, we have identified 22 cohort mortality studies of petroleum workers in the United States, the United Kingdom, Canada, and Australia. Authors of these studies were contacted, and data on the number of observed deaths and age-specific person-years of observation were requested. Data from individual studies were combined in a pooled analysis (meta-analysis). In addition to the pooled analyses, results for individual cohorts, most of which have never been reported before, are also presented. The combined multinational cohort consisted of more than 250,000 petroleum workers, and the observation period covered an interval of 55 years from 1937 to 1991. A total of 205 deaths from multiple myeloma were observed, compared to 220.93 expected, a total derived from respective national mortality rates. The corresponding standardized mortality ratio (SMR) was 0.93 and the 95% confidence interval (95% CI) was 0.81-1.07. Additional analyses were performed by type of facility and industrial process. Stratum-specific SMRs (95% CIs) were 0.92 (0.77-1.09) for refinery workers and 0.93 (0.69-1.23) for distribution workers. When individual cohorts were stratified by length of observation, no pattern was detected. The pooled analysis indicates that petroleum workers are not at an increased risk of multiple myeloma as a result of their exposure to benzene, benzene-containing liquids, or other petroleum products in their work environment. This conclusion is supported by cohort studies of workers in other industries who were exposed to benzene as well as by population-based case-control studies of multiple myeloma and occupational exposures.

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.

Risk of acute myeloid leukaemia and multiple myeloma in workers exposed to benzene

OBJECTIVE

To determine the risk of developing acute myeloid leukaemia (AML) and multiple myeloma in a cohort of workers exposed to benzene. The results were used to show the importance of taking specificity of disease into consideration in causation analysis.

METHODS

Data were derived from a cohort of workers employed at two Goodyear plants in Ohio in the manufacture of Pliofilm. Based on data in the Pliofilm study, several papers that examined the relation between exposure to benzene and leukaemia (all cell types combined) have been published. In the current analyses based on updated data in the study, standardised mortality ratios (SMRs) and 95% confidence intervals (95% CIs) were calculated for AML and multiple myeloma by cumulative exposure to benzene. The results based on AML were compared with those for leukaemia (all cell types combined) published previously.

RESULTS

An exposure response relation was shown between cumulative exposure to benzene and AML. No increased risk of AML was detected for cumulative exposure to benzene below 200 ppm-years (SMR 0.91). Above 200 ppm-years, risk of AML rose drastically; reaching a significant SMR of 98.37 for > 400 ppm-years. For multiple myeloma, no relation with exposure to benzene was detected.

CONCLUSION

Analysis specific to AML shows the importance of taking specificity of disease into consideration in causation analysis. This investigation shows that previous analyses based on all leukaemia cell types combined have incorrectly set the estimated threshold too low, and have underestimated risk above the threshold. Current regulatory policies that rely on previous analyses based on all leukaemia cell types combined should be re-examined.

Mortality among taxi drivers in Rome: a cohort study

The mortality pattern of taxi drivers in Rome as possibly exposed mainly to gasoline engine exhausts was evaluated by means of a historical cohort study. A total of 2,311 male subjects registered as taxi drivers between 1950 and 1975 was followed from 1965 through 1988. The overall mortality was lower than expected on the basis of regional (Latium) reference rates (692 deaths, standardized mortality ratio [SMR] = 0.89, 95% confidence interval [CI] 0.82-0.96), whereas the number of recorded deaths for malignant neoplasms was about the expected (205 deaths, SMR = 0.99, 95% CI 0.86-1.13). Mortality from circulatory and respiratory diseases was lower than expected. Diabetes was significantly increased (42 deaths, SMR = 1.73, 95% CI = 1.25-2.34). An increased SMR appeared for respiratory cancer (SMR = 1.23, 95% CI = 0.98-1.50), mainly due to lung cancer (observed [O] = 76, SMR = 1.23, 95% CI = 0.97-1.54); two pleural cancers were also recorded. The excess of lung cancer deaths was present only among those enrolled in the most recent period (1965-1975) (45 deaths, SMR = 1.40, 95% CI = 1.02-1.87), especially among those of younger age (< 65 years) (SMR = 1.86); there was no relation between lung cancer mortality and latency since first enrollment in the cooperatives or duration of membership. There are difficulties in interpreting the excess of lung cancer on the basis of occupational exposures; however, the increased risk observed among workers employed in more recent calendar periods may be due to heavier exposure in the last decades; further follow-up of the cohort may elucidate whether there is an increasing lung cancer risk among taxi drivers.

Carcinogenic effects of wood dust: review and discussion

Occupational exposure to wood dust (alone or chemically treated) is associated with an increased risk of developing adenocarcinoma of the nasal cavity. The specific causative agents, i.e., wood dust alone (natural products), wood dust with additives used in the processing or manufacturing of wood products, and/or physical determinants of wood dust and the associated risk factors, are not known or understood. The strongest association of exposure to wood dust and development of nasal cancer is observed in those occupations where workers are exposed to hard wood dust and chemical additives are not used. The time between first occupational exposure to wood dust and the development of adenocarcinoma of the nasal cavity averages 40 years (range 7-70 years). The epidemiological data available are not sufficient to make a definitive assessment between wood dust exposure and increased risk for cancer other than nasal cancer. The toxicity, mutagenicity, and carcinogenicity of wood dust to laboratory animals or in vitro with animal or microbial cells have not been thoroughly studied. Thus there is no direct experimental evidence on the potential hazards of wood dust. Data are insufficient or lacking on 1) wood dust exposure levels in ambient air and worker's breathing zone, and the deposition in the nasal cavity; 2) hard vs. soft wood dusts; 3) particle size and shape; 4) chemical composition of wood dust and the extent of contamination with chemical additives; and 5) interaction between inhaled wood dust, chronic irritation, and tobacco smoking. These data are required so that one can understand the association between wood dust exposure and nasal cavity tumors, along with demographic differences in cancer rates, and to develop strategies for intervention and reduction of disease causing agents in order to reduce risk to wood industry workers.

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.

Some occupational exposures as risk factors for malignant lymphomas

BACKGROUND

Malignant lymphomas (Hodgkin disease [HD] and non-Hodgkin lymphoma [NHL]) have been subject to several epidemiologic studies and found to be associated with various environmental exposures, especially solvents, wood, and phenoxy herbicides.

METHODS

Various determinants for HD and NHL were evaluated in a case-referent study encompassing 31 cases of HD, 93 cases of NHL, and 204 referents, all alive. Information on these determinants, mainly occupational exposures, was obtained by mailed questionnaires.

RESULTS

Crude odds ratios were increased for various occupational exposures, i.e., exposures to solvents, pesticides, metal fumes, welding, and fresh wood, and nursing. Further analyses based on logistic regression indicated exposure to phenoxy herbicides and fresh wood among sawmill workers, lumberjacks, and paper pulp workers to be significant risk factors for HD. Welding, working as a lumberjack, nursing, and ex-smoking were associated with a significantly increased risk for NHL. Radiographic examinations were negatively associated with HD, as was office work for NHL.

CONCLUSIONS

The results were mainly in agreement with the findings of earlier studies, but diverging associations also appeared.

A follow-up study on the mortality of truck drivers

The aim of this study was to investigate a possible relationship between occupational exposure to vehicle exhaust and cancer risk. For this purpose, a cohort of 14,225 truck drivers was followed throughout a ten-year period with regard to cause-specific mortality. Comparisons were made with another cohort of unskilled male laborers. Both of the occupational groups compared were identified at a census and no supplementary data on individual exposure history were available. The study showed an increased mortality for lung cancer (standardized mortality ratio (SMR) 160, 95% confidence interval (CI) 126-200) and multiple myeloma (SMR 439, 95% CI 142-1,024). It seems likely that exposure to diesel exhaust has contributed to the increased lung cancer risk observed. The possible relationship between multiple myeloma and certain constituents of vehicle exhaust may be worth attention in future investigations.

A case-control study of multiple myeloma and occupation

Lifetime job histories from a population-based, case-control study were analyzed to investigate the relationship between multiple myeloma and employment in various occupations and industries. Interviews were obtained from 89% (692) of eligible incident cases and 83% (1683) of eligible controls. An elevated risk was observed among persons ever employed as painters [odds ratio (OR) = 2.1, 95% confidence interval (CI) = 1.2-3.6], particularly for those employed for 10 or more years (OR = 4.1, 95% CI = 1.8-10.4). A small excess risk was observed among agricultural workers employed for 10 or more years (OR = 1.3, 95% CI = 1.0-2.2), with a higher relative risk observed among farm laborers (OR = 1.8, 95% CI = 1.0-4.0). Among agricultural workers who reported having been highly exposed to pesticides, the OR was 5.2 (95% CI = 1.6-21.1). Some evidence, based on smaller numbers, was also found to support an association with firefighting and employment in the petroleum- and coal-products manufacturing industries. Little evidence was found to support the previously noted association with wood exposure, and no evidence for an association with employment in the rubber or petroleum refining industries was found. This study lends further support to previously reported associations between multiple myeloma and employment among painters and agricultural workers.

Pesticide exposures and multiple myeloma in Iowa men

A population-based case-control study of 173 White men with multiple myeloma (MM) and 650 controls was conducted in Iowa (United States), an area with a large farming population, to evaluate the association between MM, agricultural risk factors, and exposure to individual pesticides. A slight nonsignificantly elevated risk for MM was seen among farmers (odds ratio [OR] = 1.2, 95 percent confidence interval [CI] = 0.8-1.7). Although slight excesses were observed, there were no significant associations between MM and handling either classes of pesticides or specific pesticides. Thus, this study found little evidence to suggest an association between risk of MM and farming or pesticides.

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.

Is cigarette smoking a risk factor for non-Hodgkin's lymphoma or multiple myeloma? Results from the Lutheran Brotherhood Cohort Study

Among 17,633 U.S. white male insurance policy holders whose use of tobacco was characterized in a 1966 self-administered questionnaire, there were 49 deaths from non-Hodgkin's lymphoma (NHL) and 21 from multiple myeloma (MM) during a 20-year follow-up. Men who had ever smoked cigarettes had an elevated mortality from NHL (RR = 2.1; CI = 0.9-4.9), with risk almost four-fold greater among the heaviest smokers (RR = 3.8; CI = 1.4-10.1) compared with those who used no tobacco. In contrast, risk of MM was only slightly elevated among those who had ever smoked cigarettes (RR = 1.3; CI = 0.4-3.9) and without evidence of a dose-response trend. Since this is the first cohort study suggesting a link between cigarette smoking and NHL and findings from case-control studies have been inconsistent, additional clarification should be sought from larger incidence-based cohort investigations.

A prospective study of tobacco use and multiple myeloma: evidence against an association

The relationship between the use of cigarettes and other tobacco products and the risk of multiple myeloma was examined in a cohort of nearly 250,000 American veterans followed prospectively for 26 years. Compared with men who had never tobacco, the risk of death from myeloma was not increased among current (relative risk [RR] = 0.9, 95 percent confidence interval [CI] = 0.8-1.2) or former (RR = 1.0, CI = 0.8-1.3) cigarette smokers, nor among users of chewing tobacco or snuff (RR = 1.0, CI = 0.4-2.3). Risk was only slightly and nonsignificantly increased among pipe or cigar smokers (RR = 1.2, CI = 0.9-1.5). There was no indication of increasing risk with amount of tobacco used or earlier age at first use. With over 90 percent power to detect a 30 percent increased risk of this tumor occurring among current cigarette smokers, this study provides the strongest evidence to date against an association of cigarette smoking with multiple myeloma.

Smoking and risk of non-Hodgkin's lymphoma and multiple myeloma

Population-based case-control interview studies of 622 White men with non-Hodgkin's lymphoma and 820 controls from Iowa and Minnesota (United States) and 173 White men with multiple myeloma and 452 controls from Iowa offered the opportunity to investigate the relationship of these cancers with smoking. Risks were significantly elevated for all lymphoma (odds ratio [OR] = 1.4), high-grade lymphoma (OR = 2.3), and unclassified lymphoma (OR = 2.8) for cigarette smokers. Dose-response gradients were not seen with intensity of cigarette use, but risks for these subtypes were greatest for cigarette smokers of longest duration. Similar elevations in risks were seen for tobacco users. The risk of multiple myeloma was not significantly elevated for either tobacco users or cigarette smokers. The findings from this study confirm the lack of an association between smoking and multiple myeloma and provide some support for an association between tobacco use and certain subtypes of non-Hodgkin's lymphoma.

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.