The relationship between multiple myeloma and occupational exposure to six chlorinated solvents

Global, regional and national epidemiological trends of multiple myeloma from 1990 to 2021: a systematic analysis of the Global Burden of Disease study 2021

Background

Multiple myeloma (MM) is a growing global public health challenge. Known epidemiological data suggest that MM accounts for approximately 10% of all hematologic malignancies and remains the second most common hematologic cancer worldwide. This study utilized data from the 2021 Global Burden of Diseases (GBD) study to evaluate the prevalence, incidence, mortality, disability-adjusted life years (DALYs), and attributable risk factors of MM from 1990 to 2021, and to project future trends for the next 15 years.

Methods

GBD 2021 data were analyzed to assess MM's global burden using four key epidemiological measures: prevalence, incidence, mortality, and DALYs. Estimates are reported per 100,000 population with uncertainty intervals (UI). Temporal trends were assessed through estimated annual percentage change (EAPC) and 95% confidence intervals (CI). All analyses were conducted using R version 4.2.1.

Results

From 1990 to 2021, global MM prevalence, incidence, mortality, and DALYs more than doubled, particularly among males. All Social-Demographic Index (SDI) regions showed increases in ASPR, ASIR, ASMR, and ASDR (all EAPCs >0), with the middle SDI regions exhibiting the most rapid growth. ARIMA model predictions suggest that the MM burden will continue rising over the next 15 years. The proportion of MM cases attributable to high BMI also increased globally, from 6.40% in 1990 to 7.96% in 2021. MM primarily affects older adults, with the highest incidence observed in the 70-74 age group and the highest mortality rate recorded in the same age range.

Conclusion

MM presents an escalating global health challenge. Targeted preventive interventions and improvements in diagnosis, treatment, and care are critical, especially in underdeveloped regions, to address the growing global burden of MM.

Tetrachloroethylene exposure and neurobehavioral performance among children living near multiple contamination sites

BACKGROUND

Tetrachloroethylene (PCE) is a known neurotoxicant mainly observed in populations with high level occupational exposure. Health effects of low-level community exposure are poorly understood. This study evaluated PCE exposure and neurobehavioral performance in 6 to 11-year-old children living in a community with multiple PCE contamination sites.

METHODS

This cross-sectional study recruited eighty-nine children who attended public schools in Martinsville, Indiana. PCE was measured in exhaled breath using proton transfer reaction mass spectrometry. Children were classified into three exposure groups: 'Level 1' (≤ 0.75 μg/m3), 'Level 2' (>0.75-1.90 μg/m3), and 'Level 3' (>1.90 μg/m3). A battery of tests assessed children's neurobehavioral performance related to their cognition, behavior, and academic achievement and a questionnaire collected demographic and exposure characteristics. Adjusted regression models estimated associations of PCE exposure with neurobehavioral outcomes.

RESULTS

Seventy-three participants completed data collection. The average scores for all participants on the Fluid, Total, Early Childhood Composites, Behavioral Symptoms Index, and Math Computation were significantly lower than standard scores of normative sample, with 30 % of participants having one or more scores two standard deviations worse than the standard scores. Compared to children having the lowest PCE exposure, significant inverse associations were identified for PCE exposure with Fluid Composite for Level 2 (β = -12.0 (95 % CI = -23.4, -0.6)) and Level 3 (-12.2 (-23.4, -1.0)) exposure groups, Total Composite for Level 2 (-10.1 (-19.2, -1.1)) and Level 3 (-11.8 (-20.4, -3.2)) exposure groups, and Early Childhood Composite for Level 3 exposure group (-11.0 (-18.7, -3.4)).

CONCLUSIONS

This study identified associations of PCE in exhaled breath with lower cognitive functioning, problem-solving abilities, and adaptive functioning in children. Mainly, working memory, episodic memory, processing speed, and executive function-cognitive flexibility were associated with PCE exposure. These results underscore the need for further investigations, considering the impact of low-level environmental exposure on children's neurobehavioral outcomes.

Multiple Myeloma and Occupational Risk Factors: A Narrative Review

Multiple Myeloma (MM) is a neoplastic hematologic disorder caused by the excessive proliferation of plasma cells and leads to bone lesions, anemia, and kidney failure. No definite etiology has been proposed for MM, but several environmental and genetic risk factors have been implicated so far. Exposure to pesticides, benzene, and organic solvents like methyl chloride have been considered a potential risk factor. Asbestos, ionizing radiation, and wood dust exposure have also been associated with MM. As MM is a relatively rare condition, the number of studies is insufficient, and in many studies, only a few study participants recall exposure to any agents. Therefore, establishing a definite risk factor is cumbersome and further studies with large study samples are needed. By recognizing these occupational risk factors, clinicians can encourage employees to reduce their exposure as more as possible and implement precautionary measures. In this review, we highlighted the current research on the potential association between occupational exposures and MM. Because of these studies, new regulations with the goal of occupational exposure reduction are anticipated in the future.

Occupational Exposures and Risks of Non-Hodgkin Lymphoma: A Meta-Analysis

Non-Hodgkin lymphoma (NHL) is a heterogeneous group with different types of diseases. It remains unclear as to what has led to an increase in incidences of NHL, however, chemical substance exposure is known to be one of the risk factors for the disease. Therefore, we performed a systematic review and meta-analysis including case-control, cohort, and cross-sectional observational epidemiological studies to verify the association between occupational exposure to carcinogens and NHL risk. Articles between the years 2000 and 2020 were collected. Two different reviewers performed a blind selection of the studies using the Rayyan QCRI web app. Post-completion, the selected articles were extracted and analyzed via the RedCap platform. Our review resulted in 2719 articles, of which 51 were included in the meta-analysis, resulting in an overall OR of 1.27 (95% CI 1.04-1.55). Furthermore, it was observed that the main occupation associated with the increased risk of NHL was that in which workers are exposed to pesticides. We therefore conclude that the evidence synthesis of the epidemiological literature supports an increased risk for NHL, regardless of subtype, considering occupational exposure to certain chemical compounds, mainly pesticides, benzene, and trichlorethylene, and certain classes of work, primarily in the field of agriculture.

Exposição ocupacional e câncer: uma revisão guarda-chuva

Resumo Objetivo: fornecer uma visão geral das associações entre exposição ocupacional e risco da ocorrência ou morte por câncer. Métodos: esta revisão guarda-chuva da literatura utilizou as bases Medline e Web of Science. A partir de protocolo de busca, foram incluídas metanálises para diversas circunstâncias ocupacionais e cânceres selecionados que possuíssem algum nível de evidência para associação com ocupação. Resultados: foram incluídas 37 metanálises, abrangendo 18 localizações de câncer. Considerando a avaliação da heterogeneidade dos estudos, da qualidade da evidência e da força de associação, obteve-se evidências altamente sugestivas de associações entre exposição a solvente e mieloma múltiplo; amianto e câncer de pulmão; hidrocarbonetos e câncer de trato aerodigestivo superior; e estresse ocupacional e câncer colorretal. Conclusão: há evidências robustas para associar exposições ocupacionais e tipos de câncer não previstos, inicialmente, nas orientações de vigilância do câncer relacionado ao trabalho no Brasil. Permanecem lacunas sobre exposições de grande relevância, que carecem de metanálises mais consistentes, por exemplo, exposição a poeiras inorgânicas e câncer de pulmão e mesotelioma; exposição a solventes e tumores hematológicos. Evidências de câncer em outras regiões anatômicas foram menos robustas, apresentando indícios de incerteza ou viés.

Occupational exposure and cancer: an umbrella review

Abstract Objective: to provide an overview of the associations between occupational exposure and risk of occurrence or death from cancer. Methods: this umbrella review used the Medline and Web of Science databases. Based on the search protocol, meta-analysis was included for several occupational circumstances and selected cancers that had some level of evidence associated with the occupation. Results: 37 meta-analysis were included, covering 18 cancer locations. By assessing the heterogeneity of studies, quality of evidence, and strength of association, results highly indicated associations between solvent exposure and multiple myeloma, asbestos and lung cancer, hydrocarbons and upper aerodigestive tract cancer, occupational stress and colorectal cancer. Conclusion: robust evidence shows an association between occupational exposures and types of cancer not initially foreseen in the guidelines for work-related cancer surveillance in Brazil. Gaps in relevant exposures require further research and more consistent meta-analysis, including: exposure to inorganic dust and lung cancer and mesothelioma; solvents and hematological tumors. Evidence of cancer in other anatomical regions was less robust, showing signs of uncertainty or bias.

Evaluation of the carcinogenicity of dichloromethane in rats, mice, hamsters and humans

Dichloromethane (DCM) is a high production volume chemical (>1000 t/a) mainly used as an industrial solvent. Carcinogenicity studies in rats, mice and hamsters have demonstrated a malignant tumor inducing potential of DCM only in the mouse (lung and liver) at 1000-4000 ppm whereas human data do not support a conclusion of cancer risk. Based on this, DCM has been classified as a cat. 2 carcinogen. Dose-dependent toxicokinetics of DCM suggest that DCM is a threshold carcinogen in mice, initiating carcinogenicity via the low affinity/high capacity GSTT1 pathway; a biotransformation pathway that becomes relevant only at high exposure concentrations. Rats and hamsters have very low activities of this DCM-metabolizing GST and humans have even lower activities of this enzyme. Based on the induction of specific tumors selectively in the mouse, the dose- and species-specific toxicokinetics in this species, and the absence of a malignant tumor response by DCM in rats and hamsters having a closer relationship to DCM toxicokinetics in humans and thus being a more relevant animal model, the current classification of DCM as human carcinogen cat. 2 remains appropriate.

Mortality among autoworkers manufacturing electronics in Huntsville, Alabama

BACKGROUND

Workers raised concerns over suspected excesses of mortality at automotive electronics manufacturing facilities in Huntsville, Alabama.

METHODS

A study of 4396 UAW members ever-employed at Huntsville facilities between 1972 and 1993 was conducted with mortality follow-up through 2016. Standardized Mortality Ratios (SMRs) were estimated using U.S. and Alabama reference rates.

RESULTS

Relative to U.S. rates, there was a modest excess of all-cause mortality among White female workers (SMR 1.08, 95%CI: 0.99-1.18) and among all workers hired <1977 at the original plant building (SMR 1.10, 95%CI: 0.99-1.22). There was excess nervous system disorder (SMR 1.24, 95%CI: 0.91-1.65) and brain and nervous system cancer (SMR 1.31, 95%CI: 0.67-2.28) mortality. Estimates for several causes of interest were imprecise.

CONCLUSIONS

All-cause mortality estimates were greater than anticipated based on results from other UAW cohorts. The excess of nervous system disease mortality is consistent with other studies of electronics workers exposed to lead-solder and chlorinated solvents.

Employment characteristics and cause-specific mortality at automotive electronics manufacturing plants in Huntsville, Alabama

BACKGROUND

This study was carried out in response to worker concerns over their exposure to lead solder and chlorinated solvents at automotive electronics manufacturing plants in Huntsville, Alabama.

METHODS

A study of 4396 United Autoworkers members ever-employed at the plants between 1972 and 1993 was conducted with mortality follow-up through 2016. Poisson regression was used to estimate mortality rate ratios (RR) according to employment characteristics, including calendar period of employment.

RESULTS

Pre-1977 hires exhibited elevated adjusted rates of all-cause (RR, 1.29; 95% confidence interval [CI], 1.09-1.52), cardiovascular (RR, 1.38; 95% CI, 1.03-1.86), and digestive system (RR, 2.31; 95% CI, 1.04-5.10) disease mortality relative to the most recent hire group (1984-1993). Never- versus ever-employment in a skilled trade job was associated with elevated adjusted rates of all-cause, all-cancer, and cardiovascular disease mortality. Nervous system disorder mortality was greatest among 1977-1983 hires.

CONCLUSIONS

Elevated mortality among pre-1977 hires is consistent with worker concerns over greater exposure to hazards at the original plant building.

Distribution of multiple myeloma in India: Heterogeneity in incidence across age, sex and geography

BACKGROUND

This study aimed to investigate the distribution of multiple myeloma (MM) in India and provide a comprehensive narrative about its incidence, including differential patterns across age, sex and geography.

METHODS

MM cases diagnosed during 2012-14 were obtained from 27 populations based cancer registries in India by consulting the latest National Cancer Registry Programme reports. Crude (CR) and age-specific (ASR) rates of MM incidence were determined. Age-adjusted rates (AARs) were estimated by standardizing the CR values using age-specific weights recommended for LMIC countries (including India) for men and women separately, along with the corresponding 95% confidence interval (95% CI) measures.

RESULTS

Altogether, 1916 MM cases (male/female: 1123/793) were documented (i.e. 1.19% of all cancers, 95% CI: 1.14-1.24%). Overall CR of MM in India was 1.27 (95% CI: 1.20-1.35)/ 100,000 in men and 0.95 (95% CI: 0.89-1.02)/ 100,000 in women, while the corresponding AARs were 1.13 (95% CI: 1.07-1.20) and 0.81 (95% CI: 0.75 - 0.88) per 100,000 respectively. The ASR values increased steadily with age. Most cases belonged to the 60-69 yrs bracket. However, regional and sex-specific differences in MM profile were observed. MM incidence was highest in the Southern and Northern zones, and least in the Northeast. The Northern and Central zones had higher proportion of MM in the 50-59 yrs age group, whereas Eastern zone had higher proportion of cases aged 70 yrs and above.

CONCLUSION

Incidence of MM in India is presented. Marked variations in MM incidence were noted with respect to age, sex and geography.

Multiple myeloma in paleopathology: A critical review

This paper provides a critical literature review concerning paleopathological evidence of multiple myeloma discovered both in the Old and in the New World. A critical assessment of the bioarchaeological and paleopathological documentary sources permitted to identify a total of 25 ascertained cases of multiple myeloma from different geographical areas in the world ranging from Prehistoric times up to the Contemporary age. The distribution of multiple myeloma findings in past times shows that the majority of cases have been discovered in the Old World (n = 18) and extend back to the Middle Ages, while the evidences in the New World (n = 7) seems to date back to the pre-Columbian era. The demographic profile suggests a sex ratio of 1.3:1, while 91.7% of affected individuals (n = 24) are adults. This critical review also discusses the diagnostic criteria and methodological issues commonly attempted in paleo-oncological research, with particular regard to the differential diagnosis of multiple myeloma. As such, the main focus of this work is to present a comprehensive and exhaustive scrutiny of the skeletal manifestations identified as multiple myeloma in order to improve the accuracy of diagnoses within the field of paleopathology.

Pooled study of occupational exposure to aromatic hydrocarbon solvents and risk of multiple myeloma

OBJECTIVES

To investigate the association between occupational exposure to aromatic hydrocarbon solvents and risk of multiple myeloma (MM) in a large, consortium-based study.

METHODS

We pooled data on 2854 cases and 10 743 controls from nine studies participating in the InterLymph consortium. Occupational exposures to benzene, toluene and xylene were assigned by a job-exposure matrix, coupled with 'correction' of exposure probability by self-reported or expert-assessed exposure from the individual studies. Cumulative intensity was calculated as the job-specific exposure intensity multiplied by job duration, summed across jobs. Associations were estimated using logistic regression, with inclusion of covariates for study matching factors and other potential confounders. We repeated our main analysis using random-effects meta-analysis to evaluate heterogeneity of effect.

RESULTS

Benzene, toluene and xylene were each associated with MM. For the three solvents, the highest quartile of high-probability cumulative intensity exposure (vs unexposed) was associated with 42% to 63% increased risks of MM. Associations with toluene and xylene exposures were fairly consistent and robust to sensitivity analyses. The estimated effect for benzene was moderately heterogeneous between the studies. Each solvent's association with MM was stronger for exposure occurring within 20 years of diagnosis than with exposure lagged by more than 20 years.

CONCLUSIONS

Our study adds important evidence for a role of aromatic hydrocarbon solvents in causation of MM. The difficulty in disentangling individual compounds in this group and a lack of data on potential carcinogenicity of toluene and xylene, in widespread current use, underscore a need for further epidemiological evaluation.

Bacterial Community Dynamics in Dichloromethane-Contaminated Groundwater Undergoing Natural Attenuation

The uncontrolled release of the industrial solvent methylene chloride, also known as dichloromethane (DCM), has resulted in widespread groundwater contamination in the United States. Here we investigate the role of groundwater bacterial communities in the natural attenuation of DCM at an undisclosed manufacturing site in New Jersey. This study investigates the bacterial community structure of groundwater samples differentially contaminated with DCM to better understand the biodegradation potential of these autochthonous bacterial communities. Bacterial community analysis was completed using high-throughput sequencing of the 16S rRNA gene of groundwater samples (n = 26) with DCM contamination ranging from 0.89 to 9,800,000 μg/L. Significant DCM concentration-driven shifts in overall bacterial community structure were identified between samples, including an increase in the abundance of Firmicutes within the most contaminated samples. Across all samples, a total of 6,134 unique operational taxonomic units (OTUs) were identified, with 16 taxa having strong correlations with increased DCM concentration. Putative DCM degraders such as Pseudomonas, Dehalobacterium and Desulfovibrio were present within groundwater across all levels of DCM contamination. Interestingly, each of these taxa dominated specific DCM contamination ranges respectively. Potential DCM degrading lineages yet to be cited specifically as a DCM degrading organisms, such as the Desulfosporosinus, thrived within the most heavily contaminated groundwater samples. Co-occurrence network analysis revealed aerobic and anaerobic bacterial taxa with DCM-degrading potential were present at the study site. Our 16S rRNA gene survey serves as the first in situ bacterial community assessment of contaminated groundwater harboring DCM concentrations ranging over seven orders of magnitude. Diversity analyses revealed known as well as potentially novel DCM degrading taxa within defined DCM concentration ranges, indicating niche-specific responses of these autochthonous populations. Altogether, our findings suggest that monitored natural attenuation is an appropriate remediation strategy for DCM contamination, and that high-throughput sequencing technologies are a robust method for assessing the potential role of biodegrading bacterial assemblages in the apparent reduction of DCM concentrations in environmental scenarios.

Long-term health effects of early life exposure to tetrachloroethylene (PCE)-contaminated drinking water: a retrospective cohort study

BACKGROUND

While adult exposure to PCE is known to have toxic effects, there is little information on the long-term impact of prenatal and early childhood exposure. We undertook a retrospective cohort study to examine the effects of their early life exposure to PCE-contaminated drinking water. This retrospective cohort study examined whether prenatal and early childhood exposure to PCE-contaminated drinking water influenced the risk of a variety of chronic conditions among adults who were born between 1969 and 1983 in the Cape Cod area of Massachusetts.

METHODS

Eight hundred and thirty-one participants with prenatal and early childhood PCE exposure and 547 unexposed participants were studied. Individuals completed questionnaires to gather information on demographic characteristics, chronic conditions, and other sources of solvent exposure. The location of residences from birth through 1990 were used to estimate PCE exposure with U.S. EPA's water distribution system modeling software (EPANET) modified to incorporate a leaching and transport model.

RESULTS

No associations were observed between early life PCE exposure and current occurrence of obesity, diabetes, cardiovascular disease, hypertension, color blindness, near- and far sightedness and dry eyes. In contrast, a 1.8-fold increased risk of cancer (95% CI: 0.8, 4.0) was seen among individuals with any early life exposure. These results were based on 31 participants (23 exposed and 8 unexposed) who reported cancers at a variety of anatomical sites, particularly the cervix. A 1.5-fold increase in the risk of epilepsy (95% CI: 0.6, 3.6, based on 16 exposed and 7 unexposed participants) was also observed among individuals with any early life exposure that was further increased to 1.8 (95% CI: 0.7, 4.6) among those with exposure at or above the sample median.

CONCLUSIONS

These results suggest that the risk of epilepsy and certain types of cancer such as cervical cancer may be increased among adults who were exposed to PCE-contaminated drinking water exposure during gestation and early childhood. These findings should be interpreted cautiously because of the study limitations and confirmed in follow-up investigations of similarly exposed populations with medically-confirmed diagnoses. This relatively young study population should also be monitored periodically for subsequent changes in disease risk.

Human health effects of dichloromethane: key findings and scientific issues

BACKGROUND

The U.S. EPA's Integrated Risk Information System (IRIS) completed an updated toxicological review of dichloromethane in November 2011.

OBJECTIVES

In this commentary we summarize key results and issues of this review, including exposure sources, identification of potential health effects, and updated physiologically based pharmacokinetic (PBPK) modeling.

METHODS

We performed a comprehensive review of primary research studies and evaluation of PBPK models.

DISCUSSION

Hepatotoxicity was observed in oral and inhalation exposure studies in several studies in animals; neurological effects were also identified as a potential area of concern. Dichloromethane was classified as likely to be carcinogenic in humans based primarily on evidence of carcinogenicity at two sites (liver and lung) in male and female B6C3F1 mice (inhalation exposure) and at one site (liver) in male B6C3F1 mice (drinking-water exposure). Recent epidemiologic studies of dichloromethane (seven studies of hematopoietic cancers published since 2000) provide additional data raising concerns about associations with non-Hodgkin lymphoma and multiple myeloma. Although there are gaps in the database for dichloromethane genotoxicity (i.e., DNA adduct formation and gene mutations in target tissues in vivo), the positive DNA damage assays correlated with tissue and/or species availability of functional glutathione S-transferase (GST) metabolic activity, the key activation pathway for dichloromethane-induced cancer. Innovations in the IRIS assessment include estimation of cancer risk specifically for a presumed sensitive genotype (GST-theta-1+/+), and PBPK modeling accounting for human physiological distributions based on the expected distribution for all individuals 6 months to 80 years of age.

CONCLUSION

The 2011 IRIS assessment of dichloromethane provides insights into the toxicity of a commonly used solvent.

Unusual case of simultaneous presentation of plasma cell myeloma, chronic myelogenous leukemia, and a jak2 positive myeloproliferative disorder

Background. Multiple articles discuss the rare incidence and potential causes of second hematologic disorders arising after treatment of Chronic Myelogenous Leukemia (CML), leading to the theory of imatinib, the current treatment regimen for CML, as a possible trigger for the development of secondary neoplasms. Our case eliminates the possibility of imatinib as the sole cause since our patient received a diagnosis of simultaneous plasma cell myeloma, CML, and a Jak2 mutation positive myeloproliferative disorder (MPD) arising de novo, prior to any treatment. We will further investigate into alternative theories as potential causes for multiple hematopathologic disorders. Case Report. There are currently no reported cases with the diagnosis of simultaneous plasma cell myeloma, chronic myelogenous leukemia, and Jak2 positive myeloproliferative disorder. We present a case of a 77-year-old male who was discovered to have these three concurring hematopathologic diagnoses. Our review of the literature includes a look at potential associations linking the three coexisting hematologic entities. Conclusion. The mechanism resulting in simultaneous malignancies is most likely multifactorial and potentially includes factors specific to the host, continuous stimulation of the immune system, previous chemotherapy or radiation, a potential common pluripotent stem cell, or, lastly, preexisting myeloma which may increase the susceptibility of additional malignancies.

Simultaneous occurrence of two B-cell malignancies: A case report

The present study describes the case of a 75-year-old male with coexisting multiple myeloma and diffuse large B-cell lymphoma. Although the two malignancies are mature B-cell neoplasms, their clinical manifestations are very different and the clinical approaches used to treat these two types of tumor vary. The patient in the present case was diagnosed with the simultaneous existence of two different B-cell tumors and was successfully treated using the DCEP regimen. The simultaneous presentation of two mature B-cell neoplasms, types of hematological malignancy, is very rare, thus the present case is considered to be interesting.

Human health effects of tetrachloroethylene: key findings and scientific issues

BACKGROUND

The U.S. Environmental Protection Agency (EPA) completed a toxicological review of tetrachloroethylene (perchloroethylene, PCE) in February 2012 in support of the Integrated Risk Information System (IRIS).

OBJECTIVES

We reviewed key findings and scientific issues regarding the human health effects of PCE described in the U.S. EPA's Toxicological Review of Tetrachloroethylene (Perchloroethylene).

METHODS

The updated assessment of PCE synthesized and characterized a substantial database of epidemiological, experimental animal, and mechanistic studies. Key scientific issues were addressed through modeling of PCE toxicokinetics, synthesis of evidence from neurological studies, and analyses of toxicokinetic, mechanistic, and other factors (tumor latency, severity, and background rate) in interpreting experimental animal cancer findings. Considerations in evaluating epidemiological studies included the quality (e.g., specificity) of the exposure assessment methods and other essential design features, and the potential for alternative explanations for observed associations (e.g., bias or confounding).

DISCUSSION

Toxicokinetic modeling aided in characterizing the complex metabolism and multiple metabolites that contribute to PCE toxicity. The exposure assessment approach-a key evaluation factor for epidemiological studies of bladder cancer, non-Hodgkin lymphoma, and multiple myeloma-provided suggestive evidence of carcinogenicity. Bioassay data provided conclusive evidence of carcinogenicity in experimental animals. Neurotoxicity was identified as a sensitive noncancer health effect, occurring at low exposures: a conclusion supported by multiple studies. Evidence was integrated from human, experimental animal, and mechanistic data sets in assessing adverse health effects of PCE.

CONCLUSIONS

PCE is likely to be carcinogenic to humans. Neurotoxicity is a sensitive adverse health effect of PCE.

Occupational exposure to methylene chloride and risk of cancer: a meta-analysis

METHODS

We searched MEDLINE and EMBASE for epidemiologic studies on occupational exposure to methylene chloride and risk of cancer. Estimates of study-specific odds ratios (ORs) were calculated using inverse-variance-weighted fixed-effects models and random-effects models. Statistical tests for heterogeneity were applied.

RESULTS

We summarized data from five cohort studies and 13 case-control studies. The pooled OR for multiple myeloma was (OR 2.04; 95 % CI 1.31-3.17) in relation to occupational exposure to methylene chloride but not for non-Hodgkin's lymphoma, leukemia, breast, bronchus, trachea and lung, brain and other CNS, biliary passages and liver, prostate, pancreas, and rectum. Furthermore, we focused on specific outcomes for non-Hodgkin's lymphoma and multiple myeloma because of exposure misclassification. The pooling OR for non-Hodgkin's lymphoma and multiple myeloma was 1.42 (95 % CI 1.10-1.83) with moderate degree of heterogeneity among the studies (I (2) = 26.9 %, p = 0.205).

CONCLUSIONS

We found an excess risk of multiple myeloma. The non-Hodgkin's lymphoma and leukemia that have shown weak effects should be investigated further.

Risk of selected cancers due to occupational exposure to chlorinated solvents in a case-control study in Montreal

OBJECTIVE

To evaluate the association between exposure to chlorinated solvents and cancer.

METHODS

We conducted a case-control study of occupational exposures and cancer in Montreal, Quebec, Canada, including 3730 cancer cases and 533 population controls. Occupational exposures were derived using a combination of subject-reported job history and expert assessment. We examined the associations between two chemical families and six chlorinated solvents with 11 sites of cancer.

RESULTS

The majority of the associations examined were null, although many were based on small numbers. We found two significantly elevated odds ratios (ORs), one between perchloroethylene and prostate cancer (OR = 4.3; 95% CI: 1.4 to 13) and another between trichloroethylene and melanoma (OR = 3.2; 95% CI: 1.0 to 9.9).

CONCLUSIONS

There was little evidence of associations between chlorinated solvents and cancer. Limited power precludes strong inferences about absence of risk. We raise hypotheses about two possible associations: perchloroethylene with prostate cancer and trichloroethylene with melanoma.

Multiple myeloma and occupation: a pooled analysis by the International Multiple Myeloma Consortium

OBJECTIVE

We investigated occupational risk of multiple myeloma (MM) in a pooled analysis of five international case-control studies.

METHODS

We calculated the odds ratio and its 95% confidence interval for selected occupations with unconditional regression analysis in 1959 MM cases and 6192 controls, by pooling study-specific risks using random-effects meta-analysis. Exposure to organic solvents was assessed with a job-exposure matrix (JEM).

RESULTS

Gardeners and nursery workers combined, most likely exposed to pesticides, showed a 50% increase in risk (OR = 1.50, 95% CI 0.9-2.3), while other farming jobs did not. Metal processors (OR = 1.55, 95% CI 0.9-2.3), female cleaners (OR = 1.32, 95% CI 1.0-1.8), and high level exposure to organic solvents (OR = 1.38, 95% CI 0.96-1.8) also showed moderately increased risks.

CONCLUSIONS

Additional case-control studies of MM aetiology are warranted to further investigate the nature of the repeatedly reported increase in MM risk in several occupational groups.

Comparison of two expert-based assessments of diesel exhaust exposure in a case-control study: programmable decision rules versus expert review of individual jobs

OBJECTIVES

Professional judgment is necessary to assess occupational exposure in population-based case-control studies; however, the assessments lack transparency and are time-consuming to perform. To improve transparency and efficiency, we systematically applied decision rules to questionnaire responses to assess diesel exhaust exposure in the population-based case-control New England Bladder Cancer Study.

METHODS

2631 participants reported 14 983 jobs; 2749 jobs were administered questionnaires ('modules') with diesel-relevant questions. We applied decision rules to assign exposure metrics based either on the occupational history (OH) responses (OH estimates) or on the module responses (module estimates); we then combined the separate OH and module estimates (OH/module estimates). Each job was also reviewed individually to assign exposure (one-by-one review estimates). We evaluated the agreement between the OH, OH/module and one-by-one review estimates.

RESULTS

The proportion of exposed jobs was 20-25% for all jobs, depending on approach, and 54-60% for jobs with diesel-relevant modules. The OH/module and one-by-one review estimates had moderately high agreement for all jobs (κ(w)=0.68-0.81) and for jobs with diesel-relevant modules (κ(w)=0.62-0.78) for the probability, intensity and frequency metrics. For exposed subjects, the Spearman correlation statistic was 0.72 between the cumulative OH/module and one-by-one review estimates.

CONCLUSIONS

The agreement seen here may represent an upper level of agreement because the algorithm and one-by-one review estimates were not fully independent. This study shows that applying decision-based rules can reproduce a one-by-one review, increase transparency and efficiency, and provide a mechanism to replicate exposure decisions in other studies.

Solvent exposures and Parkinson disease risk in twins

OBJECTIVE

Several case reports have linked solvent exposure to Parkinson disease (PD), but few studies have assessed associations with specific agents using an analytic epidemiologic design. We tested the hypothesis that exposure to specific solvents is associated with PD risk using a discordant twin pair design.

METHODS

Ninety-nine twin pairs discordant for PD ascertained from the National Academy of Sciences/National Research Council World War II Veteran Twins Cohort were interviewed regarding lifetime occupations and hobbies using detailed job task-specific questionnaires. Exposures to 6 specific solvents selected a priori were estimated by expert raters unaware of case status.

RESULTS

Ever exposure to trichloroethylene (TCE) was associated with significantly increased risk of PD (odds ratio [OR], 6.1; 95% confidence interval [CI] 1.2-33; p = 0.034), and exposure to perchloroethylene (PERC) and carbon tetrachloride (CCl(4) ) tended toward significance (respectively: OR, 10.5; 95% CI, 0.97-113; p = 0.053; OR, 2.3; 95% CI, 0.9-6.1; p = 0.088). Results were similar for estimates of exposure duration and cumulative lifetime exposure.

INTERPRETATION

Exposure to specific solvents may increase risk of PD. TCE is the most common organic contaminant in groundwater, and PERC and CCl(4) are also ubiquitous in the environment. Our findings require replication in other populations with well-characterized exposures, but the potential public health implications are substantial.

Second malignancies after multiple myeloma: from 1960s to 2010s

Based on small numbers, recent reports from 3 randomized trials have consistently demonstrated more hematologic malignancies in patients treated with lenalidomide as maintenance (vs placebo). This fact has prompted concern and highlighted the association between multiple myeloma and second malignancies. Furthermore, an excess of acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) after multiple myeloma has been known for over 4 decades. Most prior studies have been restricted because of small numbers of patients, inadequate follow-up, and limitations of ascertainment of second malignancies. Although the underlying biologic mechanisms of AML/MDS after multiple myeloma are unknown, treatment-related factors are presumed to be responsible. Recently, an excess risk of AML/MDS was found among 5652 patients with IgG/IgA (but not IgM) monoclonal gammopathy of undetermined significance, supporting a role for disease-related factors. Furthermore, there is evidence to suggest that polymorphisms in germline genes may contribute to a person's susceptibility to subsequent cancers, whereas the potential influence of environmental and behavioral factors remains poorly understood. This review discusses current knowledge regarding second malignancies after multiple myeloma and gives future directions for efforts designed to characterize underlying biologic mechanisms, with the goal to maximize survival and minimize the risk for second malignancies for individual patients.

Insights from epidemiology into dichloromethane and cancer risk

Dichloromethane (methylene chloride) is a widely used chlorinated solvent. We review the available epidemiology studies (five cohort studies, 13 case-control studies, including seven of hematopoietic cancers), focusing on specific cancer sites. There was little indication of an increased risk of lung cancer in the cohort studies (standardized mortality ratios ranging from 0.46 to 1.21). These cohorts are relatively small, and variable effects (e.g., point estimates ranging from 0.5 to 2.0) were seen for the rarer forms of cancers such as brain cancer and specific hematopoietic cancers. Three large population-based case-control studies of incident non-Hodgkin lymphoma in Europe and the United States observed odds ratios between 1.5 and 2.2 with dichloromethane exposure (ever exposed or highest category of exposure), with higher risk seen in specific subsets of disease. More limited indications of associations with brain cancer, breast cancer, and liver and biliary cancer were also seen in this collection of studies. Existing cohort studies, given their size and uneven exposure information, are unlikely to resolve questions of cancer risks and dichloromethane exposure. More promising approaches are population-based case-control studies of incident disease, and the combination of data from such studies, with robust exposure assessments that include detailed occupational information and exposure assignment based on industry-wide surveys or direct exposure measurements.