Gliomas and farm pesticide exposure in women: the Upper Midwest Health Study

Bisphenol A: Unveiling Its Role in Glioma Progression and Tumor Growth

Gliomas represent the most common and lethal category of primary brain tumors. Bisphenol A (BPA), a widely recognized endocrine disruptor, has been implicated in the progression of cancer. Despite its established links to various cancers, the association between BPA and glioma progression remains to be clearly defined. This study aimed to shed light on the impact of BPA on glioma cell proliferation and overall tumor progression. Our results demonstrate that BPA significantly accelerates glioma cell proliferation in a time- and dose-dependent manner. Furthermore, BPA has been found to enhance the invasive and migratory capabilities of glioma cells, potentially promoting epithelial-mesenchymal transition (EMT) characteristics within these tumors. Employing bioinformatics approaches, we devised a risk assessment model to gauge the potential glioma hazards associated with BPA exposure. Our comprehensive analysis revealed that BPA not only facilitates glioma invasion and migration but also inhibits apoptotic processes. In summary, our study offers valuable insights into the mechanisms by which BPA may promote tumorigenesis in gliomas, contributing to the understanding of its broader implications in oncology.

Occupational Cancers among Employed Women: A Narrative Review

The facts that occupational cancer in women is under-investigated, with few in-depth analyses are well known. In recent decades the workforce has changed, with an increasing number of women employed. Therefore, the inclusion of women in occupational cancer studies has become more urgent and feasible than in the past decades. The difficulties to evaluate occupational causes of female gynecologic tumors in most past cohorts and the potential variation in outcome responses between men and women must be taken into consideration. This narrative review discusses women's occupational cancer as a current area of research, focusing on three groups of workers characterized by peculiar exposure to occupational carcinogens and where women are often employed: beauticians and hairdressers; farmers; and healthcare workers. We discuss the most relevant cancers in each working category, with a particular focus on female breast cancer. In the three industries reviewed in detail, there are some risk factors which may affect primarily women, inducing breast cancer and cervical cancer, as well as risk factors that are carcinogenic in both genders, but whose effects are less well known in women.

Epidemiology meets toxicogenomics: Mining toxicologic evidence in support of an untargeted analysis of pesticides exposure and Parkinson's disease

BACKGROUND

Pesticides have been widely used in agriculture for more than half a century. However, with thousands currently in use, most have not been adequately assessed for influence Parkinson's disease (PD).

OBJECTIVES

Here we aimed to assess biologic plausibility of 70 pesticides implicated with PD through an agnostic pesticide-wide association study using a data mining approach linking toxicology and toxicogenomics databases.

METHODS

We linked the 70 targeted pesticides to quantitative high-throughput screening assay findings from the Toxicology in the 21st Century (Tox21) program and pesticide-related genetic/disease information with the Comparative Toxicogenomics Database (CTD). We used the CTD to determine networks of genes each pesticide has been linked to and assess enrichment of relevant gene ontology (GO) annotations. With Tox21, we evaluated pesticide induced activity on a series of 43 nuclear receptor and stress response assays and two cytotoxicity assays.

RESULTS

Overall, 59 % of the 70 pesticides had chemical-gene networks including at least one PD gene/gene product. In total, 41 % of the pesticides had chemical-gene networks enriched for ≥ 1 high-priority PD GO terms. For instance, 23 pesticides had chemical-gene networks enriched for response to oxidative stress, 21 for regulation of neuron death, and twelve for autophagy, including copper sulfate, endosulfan and chlorpyrifos. Of the pesticides tested against the Tox21 assays, 79 % showed activity on ≥ 1 assay and 11 were toxic to the two human cell lines. The set of PD-associated pesticides showed more activity than expected on assays testing for xenobiotic homeostasis, mitochondrial membrane permeability, and genotoxic stress.

CONCLUSIONS

Overall, cross-database queries allowed us to connect a targeted set of pesticides implicated in PD via epidemiology to specific biologic targets relevant to PD etiology. This knowledge can be used to help prioritize targets for future experimental studies and improve our understanding of the role of pesticides in PD etiology.

Pesticide Residue Intake From Fruit and Vegetable Consumption and Risk of Glioma

We aimed to determine whether intake of pesticide residues from fruits and vegetables was associated with glioma. Within 3 prospective cohorts from 1998-2016-the Nurses' Health Study (NHS), Nurses' Health Study II (NHSII), and Health Professionals Follow-up Study-we computed multivariable-adjusted hazard ratios (MVHRs) and 95% confidence intervals (CI) for glioma by quintiles of intake of low- and high-pesticide-residue fruits and vegetables using Cox proportional hazards regression. Fruits and vegetables were categorized as high or low residue using a validated method based on pesticide surveillance data. We confirmed 275 glioma cases across 2,745,862 person-years. A significant association was observed between intake of high-residue fruits and vegetables and glioma in NHS (MVHR = 2.99, 95% CI: 1.38, 6.44 comparing highest with lowest quintile, P for trend = 0.02). This was not identified in NHSII (MVHR = 0.52, 95% CI: 0.19, 1.45, P for trend = 0.20) or Health Professionals Follow-up Study (MVHR = 1.01, 95% CI: 0.42, 2.45, P for trend = 0.39). No significant associations were observed by intake of low-residue fruits and vegetables; overall intake was not significantly associated with glioma in any cohort. We found no evidence for an inverse relationship of fruit and vegetable intake with glioma. Although limited in power, this study suggests a possible association between fruit-and-vegetable pesticide residue intake and risk of glioma that merits further study.

The Multifaceted Role of Extracellular Vesicles in Glioblastoma: microRNA Nanocarriers for Disease Progression and Gene Therapy

Glioblastoma (GB) is the most aggressive form of brain cancer in adults, characterized by poor survival rates and lack of effective therapies. MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression post-transcriptionally through specific pairing with target messenger RNAs (mRNAs). Extracellular vesicles (EVs), a heterogeneous group of cell-derived vesicles, transport miRNAs, mRNAs and intracellular proteins, and have been shown to promote horizontal malignancy into adjacent tissue, as well as resistance to conventional therapies. Furthermore, GB-derived EVs have distinct miRNA contents and are able to penetrate the blood-brain barrier. Numerous studies have attempted to identify EV-associated miRNA biomarkers in serum/plasma and cerebrospinal fluid, but their collective findings fail to identify reliable biomarkers that can be applied in clinical settings. However, EVs carrying specific miRNAs or miRNA inhibitors have great potential as therapeutic nanotools in GB, and several studies have investigated this possibility on in vitro and in vivo models. In this review, we discuss the role of EVs and their miRNA content in GB progression and resistance to therapy, with emphasis on their potential as diagnostic, prognostic and disease monitoring biomarkers and as nanocarriers for gene therapy.

Occupational exposure to pesticides and central nervous system tumors: results from the CERENAT case-control study

BACKGROUND

The etiology of the central nervous system (CNS) tumors remains largely unknown. The role of pesticide exposure has been suggested by several epidemiological studies, but with no definitive conclusion.

OBJECTIVE

To analyze associations between occupational pesticide exposure and primary CNS tumors in adults in the CERENAT study.

METHODS

CERENAT is a multicenter case-control study conducted in France in 2004-2006. Data about occupational pesticide uses-in and outside agriculture-were collected during detailed face-to-face interviews and reviewed by experts for consistency and exposure assignment. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated with conditional logistic regression.

RESULTS

A total of 596 cases (273 gliomas, 218 meningiomas, 105 others) and 1 192 age- and sex-matched controls selected in the general population were analyzed. Direct and indirect exposures to pesticides in agriculture were respectively assigned to 125 (7.0%) and 629 (35.2%) individuals and exposure outside agriculture to 146 (8.2%) individuals. For overall agricultural exposure, we observed no increase in risk for all brain tumors (OR 1.04, 0.69-1.57) and a slight increase for gliomas (OR 1.37, 0.79-2.39). Risks for gliomas were higher when considering agricultural exposure for more than 10 years (OR 2.22, 0.94-5.24) and significantly trebled in open field agriculture (OR 3.58, 1.20-10.70). Increases in risk were also observed in non-agricultural exposures, especially in green space workers who were directly exposed (OR 1.89, 0.82-4.39), and these were statistically significant for those exposed for over 10 years (OR 2.84, 1.15-6.99).

DISCUSSION

These data support some previous findings regarding the potential role of occupational exposures to pesticides in CNS tumors, both inside and outside agriculture.

Agricultural exposures to carbamate herbicides and fungicides and central nervous system tumour incidence in the cohort AGRICAN

BACKGROUND

Pesticides exposures could be implicated in the excess of Central Nervous System (CNS) tumors observed in farmers, but evidence concerning individual pesticides remains limited. Carbamate derivative pesticides, including herbicides and fungicides (i.e. (thio/dithio)-carbamates), have shown evidence of carcinogenicity in experimental studies in animals. In the French AGRICAN cohort, we assessed the associations between potential exposures to carbamate herbicides and fungicides and the incidence of CNS tumors, overall and by histological subtype.

METHODS

AGRICAN enrolled 181,842 participants involved in agriculture. Incident CNS tumors were identified by linkage with cancer registries from enrollment (2005-2007) until 2013. Individual exposures were assessed by combining information on lifetime periods of pesticide use on crops and the French crop-exposure matrix PESTIMAT, for each of the 14 carbamate and thiocarbamate herbicides and the 16 carbamate and dithiocarbamate fungicides registered in France since 1950. Associations were estimated using proportional hazard models with age as the underlying timescale, adjusting for gender, educational level and smoking.

RESULTS

During an average follow-up of 6.9 years, 381 incident cases of CNS tumors occurred, including 164 gliomas and 134 meningiomas. Analyses showed increased risks of CNS tumors with overall exposure to carbamate fungicides (Hazard Ratio, HR = 1.88; 95% CI: 1.27-2.79) and, to a lesser extent, to carbamate herbicides (HR = 1.44; 95% CI: 0.94-2.22). Positive associations were observed with specific carbamates, including some fungicides (mancozeb, maneb, metiram) and herbicides (chlorpropham, propham, diallate) already suspected of being carcinogens in humans.

CONCLUSIONS

Although some associations need to be corroborate in further studies and should be interpreted cautiously, these findings provide additional carcinogenicity evidence for several carbamate fungicides and herbicides.

An algorithm for quantitatively estimating non-occupational pesticide exposure intensity for spouses in the Agricultural Health Study

Residents of agricultural areas experience pesticide exposures from sources other than direct agricultural work. We developed a quantitative, active ingredient-specific algorithm for cumulative (adult, married lifetime) non-occupational pesticide exposure intensity for spouses of farmers who applied pesticides in the Agricultural Health Study (AHS). The algorithm addressed three exposure pathways: take-home, agricultural drift, and residential pesticide use. Pathway-specific equations combined (i) weights derived from previous meta-analyses of published pesticide exposure data and (ii) information from the questionnaire on frequency and duration of pesticide use by applicators, home proximity to treated fields, residential pesticide usage (e.g., termite treatments), and spouse's off-farm employment (proxy for time at home). The residential use equation also incorporated a published probability matrix that documented the likelihood active ingredients were used in home pest treatment products. We illustrate use of these equations by calculating exposure intensities for the insecticide chlorpyrifos and herbicide atrazine for 19,959 spouses. Non-zero estimates for ≥1 pathway were found for 78% and 77% of spouses for chlorpyrifos and atrazine, respectively. Variability in exposed spouses' intensity estimates was observed for both pesticides, with 75th to 25th percentile ratios ranging from 7.1 to 7.3 for take-home, 6.5 to 8.5 for drift, 2.4 to 2.8 for residential use, and 3.8 to 7.0 for the summed pathways. Take-home and drift estimates were highly correlated (≥0.98), but were not correlated with residential use (0.01‒0.02). This algorithm represents an important advancement in quantifying non-occupational pesticide relative exposure differences and will facilitate improved etiologic analyses in the AHS spouses. The algorithm could be adapted to studies with similar information.

Beneficial role of vanillin, a polyphenolic flavoring agent, on maneb-induced oxidative stress, DNA damage, and liver histological changes in Swiss albino mice

Vanillin, a widely used flavoring agent, has antimutagenic and antioxidant properties. The current study was performed to evaluate its beneficial role against hepatotoxicity induced by maneb, a dithiocarbamate fungicide. Mice were divided into four groups of six each: group 1, serving as negative controls which received by intraperitoneal way only distilled water, a solvent of maneb; group 2, received daily, by intraperitoneal way, maneb (30 mg kg^-1 body weight (BW)); group 3, received maneb at the same dose of group 2 and 50 mg kg^-1 BW of vanillin by intraperitoneal way; and group 4, serving as positive controls, received daily only vanillin. After 10 days of treatment, mice of all groups were killed. Our results showed that vanillin significantly reduced the elevated hepatic levels of malondialdehyde, hydrogen peroxide, and advanced oxidation protein product and attenuated DNA fragmentation induced by maneb. In addition, vanillin modulated the alterations of antioxidant status: enzymatic (superoxide dismutase, catalase, and glutathione peroxidase) and nonenzymatic (reduced glutathione, nonprotein thiol, and vitamin C) antioxidants in the liver of maneb-treated mice. This natural compound was also able to ameliorate plasma biochemical parameters (aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transpeptidase, alkaline phosphatase, total bilirubin, and total protein). The protective effect of vanillin was further evident through the histopathological changes produced by maneb in the liver tissue. Thus, we concluded that vanillin might be beneficial against maneb-induced hepatic damage in mice.

A prospective study of cancer risk among Agricultural Health Study farm spouses associated with personal use of organochlorine insecticides

BACKGROUND

Organochlorine insecticides (OCs) have historically been used worldwide to control insects, although most have now been banned in developed countries. Evidence for an association between OC exposures and cancer predominantly comes from occupational and population based-studies among men. We evaluated the association between the use of specific OCs and cancer among the female spouses of pesticide applicators in the Agricultural Health Study.

METHODS

At enrollment (1993-1997), spouses of private applicators in the cohort provided information about their own use of pesticides, including seven OCs (aldrin, chlordane, dieldrin, DDT, heptachlor, lindane, and toxaphene), and information on potential confounders. We used Poisson regression to estimate relative risks (RRs) and 95% confidence intervals (CIs) for cancers (n ≥ 3 exposed cases) reported to state cancer registries from enrollment through 2012 (North Carolina) and 2013 (Iowa), and use of the individual OCs, as well as use of any of the specific OCs.

RESULTS

Among 28,909 female spouses, 2191 (7.58%) reported ever use of at least one OC, of whom 287 were diagnosed with cancer. Most cancers were not associated with OC use. Risk of glioma was increased among users of at least one OC (Nexposed = 11, RR = 3.52, 95% CI 1.72-7.21) and specifically among lindane users (Nexposed = 3, RR = 4.45, 95% CI 1.36-14.55). Multiple myeloma was associated with chlordane (Nexposed = 6, RR = 2.71, 95% CI 1.12-6.55). Based on 3 exposed cases each, there were also positive associations between pancreatic cancer and lindane, and ER-PR- breast cancer and dieldrin. No other associations with breast cancer were found.

CONCLUSIONS

Overall, there were some associations with OC use and cancer incidence, however we were limited by the small number of exposed cancer cases. Future research should attempt to expand on these findings by assessing environmental sources of OC exposures, to fully evaluate the role of OC exposures on cancer risk in women.

Central nervous system tumors and agricultural exposures in the prospective cohort AGRICAN

Studies in farmers suggest a possible role of pesticides in the occurrence of Central Nervous System (CNS) tumors but scientific evidence is still insufficient. Using data from the French prospective agricultural cohort AGRICAN (Agriculture & Cancer), we investigated the associations between exposure of farmers and pesticide users to various kinds of crops and animal farming and the incidence of CNS tumors, overall and by subtypes. Over the 2005-2007, 181,842 participants completed the enrollment questionnaire that collected a complete job calendar with lifetime history of farming types. Associations were estimated using proportional hazards models with age as underlying timescale. During a 5.2 years average follow-up, 273 incident cases of CNS tumors occurred, including 126 gliomas and 87 meningiomas. Analyses showed several increased risks of CNS tumors in farmers, especially in pesticide users (hazard ratio = 1.96; 95% confidence interval: 1.11-3.47). Associations varied with tumor subtypes and kinds of crop and animal farming. The main increases in risk were observed for meningiomas in pig farmers and in farmers growing sunflowers, beets and potatoes and for gliomas in farmers growing grasslands. In most cases, more pronounced risk excesses were observed among pesticide applicators. Even if we cannot completely rule out the contribution of other factors, pesticide exposures could be of primary concern to explain these findings.

Relationship between Urinary Pesticide Residue Levels and Neurotoxic Symptoms among Women on Farms in the Western Cape, South Africa

Background: This cross-sectional study aimed to investigate the relationship between urinary pesticide residue levels and neurotoxic symptoms amongst women working on Western Cape farms in South Africa. Method: A total of 211 women were recruited from farms (n = 121) and neighbouring towns (n = 90). Participant assessment was via a Q16 questionnaire, reporting on pesticide exposures and measurement of urinary OP metabolite concentrations of dialkyl phosphates (DAP) and chlorpyriphos, 3,5,6-trichloropyridinol (TCPY) and of pyrethroid (PYR) metabolite concentrations (3- phenoxybenzoic acid (3PBA), 4-fluoro-3-phenoxybenzoic acid (4F3PBA), cis-2,2-dibromovinyl-2,2-dimethylcyclopropane-1-carboxylic acid (DBCA), and the cis- and trans isomers of 2,2-dichlorovinyl-2,2-dimethylcyclopropane-1-carboxylic acid. Results: Median urinary pesticide metabolites were slightly (6%–49%) elevated in the farm group compared to the town group, with 2 metabolites significantly higher and some lower in the farm group. The prevalence of all Q16 symptoms was higher amongst farm women compared to town women. Three Q16 symptoms (problems with buttoning, reading and notes) were significantly positively associated with three pyrethroid metabolites (cis- and trans-DCCA and DBCA), although associations may due to chance as multiple comparisons were made. The strongest association for a pyrethroid metabolite was between problems with buttoning and DBCA (odds ratio (OR) = 8.93, 95% confidence interval (CI):1.71–46.5. There was no association between Q16 symptoms and OP metabolites. Conclusions: Women farm residents and rural women from neighbouring towns in the Western Cape are exposed to OP and PYR pesticides. The study did not provide strong evidence that pesticides are associated with neurotoxic symptoms but associations found could be explored further.

The epidemiology of glioma in adults: a "state of the science" review

Gliomas are the most common primary intracranial tumor, representing 81% of malignant brain tumors. Although relatively rare, they cause significant mortality and morbidity. Glioblastoma, the most common glioma histology (∼45% of all gliomas), has a 5-year relative survival of ∼5%. A small portion of these tumors are caused by Mendelian disorders, including neurofibromatosis, tuberous sclerosis, and Li-Fraumeni syndrome. Genomic analyses of glioma have also produced new evidence about risk and prognosis. Recently discovered biomarkers that indicate improved survival include O⁶-methylguanine-DNA methyltransferase methylation, isocitrate dehydrogenase mutation, and a glioma cytosine-phosphate-guanine island methylator phenotype. Genome-wide association studies have identified heritable risk alleles within 7 genes that are associated with increased risk of glioma. Many risk factors have been examined as potential contributors to glioma risk. Most significantly, these include an increase in risk by exposure to ionizing radiation and a decrease in risk by history of allergies or atopic disease(s). The potential influence of occupational exposures and cellular phones has also been examined, with inconclusive results. We provide a “state of the science” review of current research into causes and risk factors for gliomas in adults.

HealthViEWS: mortality study of female US Vietnam era veterans, 1965-2010

We conducted a retrospective study among 4,734 women who served in the US military in Vietnam (Vietnam cohort), 2,062 women who served in countries near Vietnam (near-Vietnam cohort), and 5,313 nondeployed US military women (US cohort) to evaluate the associations of mortality outcomes with Vietnam War service. Veterans were identified from military records and followed for 40 years through December 31, 2010. Information on underlying causes of death was obtained from death certificates and the National Death Index. Based on 2,743 deaths, all 3 veteran cohorts had lower mortality risk from all causes combined and from several major causes, such as diabetes mellitus, heart disease, chronic obstructive pulmonary disease, and nervous system disease relative to comparable US women. However, excess deaths from motor vehicle accidents were observed in the Vietnam cohort (standardized mortality ratio = 3.67, 95% confidence interval (CI): 2.30, 5.56) and in the US cohort (standardized mortality ratio = 1.91, 95% CI: 1.02, 3.27). More than two-thirds of women in the study were military nurses. Nurses in the Vietnam cohort had a 2-fold higher risk of pancreatic cancer death (adjusted relative risk = 2.07, 95% CI: 1.00, 4.25) and an almost 5-fold higher risk of brain cancer death compared with nurses in the US cohort (adjusted relative risk = 4.61, 95% CI: 1.27, 16.83). Findings of all-cause and motor vehicle accident deaths among female Vietnam veterans were consistent with patterns of postwar mortality risk among other war veterans.

The Upper Midwest Health Study: industry and occupation of glioma cases and controls

BACKGROUND

Understanding glioma etiology requires determining which environmental factors are associated with glioma. Upper Midwest Health Study case-control participant work histories collected 1995-1998 were evaluated for occupational associations with glioma. "Exposures of interest" from our study protocol comprise our a priori hypotheses.

MATERIALS AND METHODS

Year-long or longer jobs for 1,973 participants were assigned Standard Occupational Classifications (SOC) and Standard Industrial Classifications (SIC). The analysis file includes 8,078 SIC- and SOC-coded jobs. For each individual, SAS 9.2 programs collated employment with identical SIC-SOC coding. Distributions of longest "total employment duration" (total years worked in jobs with identical industry and occupation codes, including multiple jobs, and non-consecutive jobs) were compared between cases and controls, using an industrial hygiene algorithm to group occupations.

RESULTS

Longest employment duration was calculated for 780 cases and 1,156 controls. More case than control longest total employment duration was in the "engineer, architect" occupational group [16 cases, 10 controls, odds ratio (OR) 2.50, adjusted for age group, sex, age and education, 95% confidence interval (CI) 1.12-5.60]. Employment as a food processing worker [mostly butchers and meat cutters] was of borderline significance (27 cases, 21 controls, adjusted OR: 1.78, CI: 0.99-3.18).

CONCLUSIONS

Among our exposures of interest work as engineers or as butchers and meat cutters was associated with increased glioma risk. Significant associations could be due to chance, because of multiple comparisons, but similar findings have been reported for other glioma studies. Our results suggest some possible associations but by themselves could not provide conclusive evidence.

Review of 2,4-dichlorophenoxyacetic acid (2,4-D) biomonitoring and epidemiology

A qualitative review of the epidemiological literature on the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and health after 2001 is presented. In order to compare the exposure of the general population, bystanders and occupational groups, their urinary levels were also reviewed. In the general population, 2,4-D exposure is at or near the level of detection (LOD). Among individuals with indirect exposure, i.e. bystanders, the urinary 2,4-D levels were also very low except in individuals with opportunity for direct contact with the herbicide. Occupational exposure, where exposure was highest, was positively correlated with behaviors related to the mixing, loading and applying process and use of personal protection. Information from biomonitoring studies increases our understanding of the validity of the exposure estimates used in epidemiology studies. The 2,4-D epidemiology literature after 2001 is broad and includes studies of cancer, reproductive toxicity, genotoxicity, and neurotoxicity. In general, a few publications have reported statistically significant associations. However, most lack precision and the results are not replicated in other independent studies. In the context of biomonitoring, the epidemiology data give no convincing or consistent evidence for any chronic adverse effect of 2,4-D in humans.

Epidemiologic studies of glyphosate and cancer: a review

The United States Environmental Protection Agency and other regulatory agencies around the world have registered glyphosate as a broad-spectrum herbicide for use on multiple food and non-food use crops. Glyphosate is widely considered by regulatory authorities and scientific bodies to have no carcinogenic potential, based primarily on results of carcinogenicity studies of rats and mice. To examine potential cancer risks in humans, we reviewed the epidemiologic literature to evaluate whether exposure to glyphosate is associated causally with cancer risk in humans. We also reviewed relevant methodological and biomonitoring studies of glyphosate. Seven cohort studies and fourteen case-control studies examined the association between glyphosate and one or more cancer outcomes. Our review found no consistent pattern of positive associations indicating a causal relationship between total cancer (in adults or children) or any site-specific cancer and exposure to glyphosate. Data from biomonitoring studies underscore the importance of exposure assessment in epidemiologic studies, and indicate that studies should incorporate not only duration and frequency of pesticide use, but also type of pesticide formulation. Because generic exposure assessments likely lead to exposure misclassification, it is recommended that exposure algorithms be validated with biomonitoring data.

The Upper Midwest Health Study: a case-control study of pesticide applicators and risk of glioma

BACKGROUND

An excess incidence of brain cancer in farmers has been noted in several studies. The National Institute for Occupational Safety and Health developed the Upper Midwest Health Study (UMHS) as a case-control study of intracranial gliomas and pesticide uses among rural residents. Previous studies of UMHS participants, using "ever-never" exposure to farm pesticides and analyzing men and women separately, found no positive association of farm pesticide exposure and glioma risks. The primary objective was to determine if quantitatively estimated exposure of pesticide applicators was associated with an increased risk of glioma in male and female participants.

METHODS

The study included 798 histologically confirmed primary intracranial glioma cases (45 % with proxy respondents) and 1,175 population-based controls, all adult (age 18-80) non-metropolitan residents of Iowa, Michigan, Minnesota, and Wisconsin. The analyses used quantitatively estimated exposure from questionnaire responses evaluated by an experienced industrial hygienist with 25 years of work on farm pesticide analyses. Odds ratios (ORs) and 95 % confidence intervals (CIs) using unconditional logistic regression modeling were calculated adjusting for frequency-matching variables (10-year age group and sex), and for age and education (a surrogate for socioeconomic status). Analyses were separately conducted with or without proxy respondents.

RESULTS

No significant positive associations with glioma were observed with cumulative years or estimated lifetime cumulative exposure of farm pesticide use. There was, a significant inverse association for phenoxy pesticide used on the farm (OR 0.96 per 10 g-years of cumulative exposure, CI 0.93-0.99). No significant findings were observed when proxy respondents were excluded. Non-farm occupational applicators of any pesticide had decreased glioma risk: OR 0.72, CI 0.52-0.99. Similarly, house and garden pesticide applicators had a decreased risk of glioma: OR 0.79, CI 0.66-0.93, with statistically significant inverse associations for use of 2,4-D, arsenates, organophosphates, and phenoxys.

CONCLUSIONS

These results are consistent with our previous findings for UMHS of reported farm pesticide exposure and support a lack of positive association between pesticides and glioma.

Should atrazine and related chlorotriazines be considered carcinogenic for human health risk assessment?

Chloro-s-triazines have been a mainstay of preemergent pesticides for a number of decades and have generally been regarded as having low human toxicity. Atrazine, the major pesticide in this class, has been extensively studied. In a number of experimental studies, exposure to high doses of atrazine resulted in increased weight loss not attributable to decreased food intake. Chronic studies of atrazine and simazine and their common metabolites show an elevated incidence of mammary tumors only in female Sprague Dawley (SD) rats. On the basis of the clear tumor increase in female SD rats, atrazine was proposed to be classified as a likely human carcinogen by US Environmental Protection Agency (EPA) in 1999. With Fischer rats, all strains of mice, and dogs, there was no evidence of increased incidence of atrazine-associated tumors of any type. Evidence related to the pivotal role of hormonal control of the estrus cycle in SD rats appears to indicate that the mechanism for mammary tumor induction is specific to this strain of rats and thus is not relevant to humans. In humans the menstrual cycle is controlled by estrogen released by the ovary rather than depending on the LH surge, as estrus is in SD rats. However, the relevance of the tumors to humans continues to be debated based on endocrine effects of triazines. No strong evidence exists for atrazine mutagenicity, while there is evidence of clastogenicity at elevated concentrations. Atrazine does not appear to interact strongly with estrogen receptors α or β but may interact with putative estrogen receptor GPR30 (G-protein-coupled receptor). A large number of epidemiologic studies conducted on manufacturing workers, pesticide applicators, and farming families do not indicate that triazines are carcinogenic in these populations. A rat-specific hormonal mechanism for mammary tumors has now been accepted by US EPA, International Agency for Research on Cancer, and the European Union. Chlorotriazines do influence endocrine responses, but their potential impact on humans appears to be primarily on reproduction and development and is not related to carcinogenesis.

Two common nonsynonymous paraoxonase 1 (PON1) gene polymorphisms and brain astrocytoma and meningioma

BACKGROUND

Human serum paraoxonase 1 (PON1) plays a major role in the metabolism of several organophosphorus compounds. The enzyme is encoded by the polymorphic gene PON1, located on chromosome 7q21.3. Aiming to identify genetic variations related to the risk of developing brain tumors, we investigated the putative association between common nonsynonymous PON1 polymorphisms and the risk of developing astrocytoma and meningioma.

METHODS

Seventy one consecutive patients with brain tumors (43 with astrocytoma grade II/III and 28 with meningioma) with ages ranging 21 to 76 years, and 220 healthy controls subjects were analyzed for the frequency of the nonsynonymous PON1 genotypes L55M rs854560 and Q192R rs662. All participants were adult Caucasian individuals recruited in the central area of Spain.

RESULTS

The frequencies of the PON1 genotypes and allelic variants of the polymorphisms PON1 L55M and PON1 Q192R did not differ significantly between patients with astrocytoma and meningioma and controls. The minor allele frequencies were as follows: PON1 55L, 0.398, 0.328 and 0.286 for patients with astrocytoma, meningioma and control individuals, respectively; PON1 192R, 0.341, 0.362 and 0.302 for patients with astrocytoma, meningioma and control individuals, respectively. Correction for age, gender, or education, made no difference in odds ratios and the p values remained non-significant. Haplotype association analyses did not identify any significant association with the risk of developing astrocytoma or meningioma.

CONCLUSIONS

Common nonsynonymous PON1 polymorphisms are not related with the risk of developing astrocytoma and meningioma.

Occupational and environmental risk factors for brain cancer: a pilot case-control study in France

INTRODUCTION

The increased incidence of malignant primary brain tumors (MPBT) reported in several studies could be due to environmental factors. To estimate the chemical and physical risk factors of these tumors in southeastern France, a pilot case-control study that included all new MPBT cases diagnosed in 2005 in the main brain cancer treatment centers in the western section of the Provence-Alpes-Côte d'Azur (PACA) region.

MATERIAL AND METHODS

Age-, sex-, and hospital-matched controls were selected from the neurosurgery department of the same hospital. An occupational physician, using a standardized questionnaire, collected information on suspected risk factors of MPBT in a face-to-face interview at the hospital of all case and control subjects. Data collected included jobs held, various exposures throughout working life, and leisure time activities.

RESULTS

The study included 122 cases and 122 controls. No particular job was identified as a major risk factor for brain cancer. Risk was significantly higher among those who used glue (OR=17.58, 95% CI 1.75 - 176.62) during leisure activities and significantly lower among those residing near cellular telephone towers (OR=0.49, 95% CI 0.26 - 0.92).

DISCUSSION

Several new hypotheses about the effects of cellular telephone towers and chemical exposure merit further analytic studies.

Exposure to farm crops, livestock, and farm tasks and risk of glioma: the Upper Midwest Health Study

Some studies of brain cancer have found an excess risk for farmers. The National Institute for Occupational Safety and Health previously found no increased glioma risk for ever (vs. never) being exposed to pesticides on a farm among 798 cases and 1,175 population-based controls (adult (ages 18-80 years) nonmetropolitan residents of Iowa, Michigan, Minnesota, and Wisconsin). For this analysis (1995-1998), 288 cases and 474 controls (or their proxies) who had lived on farms at age 18 years or after were asked about exposure to crops, livestock, and farm tasks. Logistic regression was used to calculate odds ratios adjusted for age, age group, sex, state, and education. Never immediately washing up (adjusted odds ratio (OR) = 3.08, 95% confidence interval (CI): 1.78, 5.34) or changing clothes (OR = 2.84, 95% CI: 1.04, 7.78) after applying pesticides was associated with increased glioma risk. Living on a farm on which corn, oats, soybeans, or hogs were raised was associated with decreased risk (corn-OR = 0.37, 95% CI: 0.20, 0.69; oats-OR = 0.63, 95% CI: 0.40, 1.00; soybeans-OR = 0.69, 95% CI: 0.48, 0.98; hogs-OR = 0.63, 95% CI: 0.43, 0.93). Negative associations may be due to chance or a "healthy farmer" effect. Farmers' increased risk of glioma may be due to work practices, other activities, or an inverse association with allergies (reported by other investigators).

Associations between polymorphisms in DNA repair genes and glioblastoma

A pooled analysis was conducted to examine the association between select variants in DNA repair genes and glioblastoma multiforme, the most common and deadliest form of adult brain tumors. Genetic data for approximately 1,000 glioblastoma multiforme cases and 2,000 controls were combined from four centers in the United States that have conducted case-control studies on adult glioblastoma multiforme, including the National Cancer Institute, the National Institute for Occupational Safety and Health, the University of Texas M. D. Anderson Cancer Center, and the University of California at San Francisco. Twelve DNA repair single-nucleotide polymorphisms were selected for investigation in the pilot collaborative project. The C allele of the PARP1 rs1136410 variant was associated with a 20% reduction in risk for glioblastoma multiforme (odds ratio(CT or CC), 0.80; 95% confidence interval, 0.67-0.95). A 44% increase in risk for glioblastoma multiforme was found for individuals homozygous for the G allele of the PRKDC rs7003908 variant (odds ratio(GG), 1.44; 95% confidence interval, 1.13-1.84); there was a statistically significant trend (P = 0.009) with increasing number of G alleles. A significant, protective effect was found when three single-nucleotide polymorphisms (ERCC2 rs13181, ERCC1 rs3212986, and GLTSCR1 rs1035938) located near each other on chromosome 19 were modeled as a haplotype. The most common haplotype (AGC) was associated with a 23% reduction in risk (P = 0.03) compared with all other haplotypes combined. Few studies have reported on the associations between variants in DNA repair genes and brain tumors, and few specifically have examined their impact on glioblastoma multiforme. Our results suggest that common variation in DNA repair genes may be associated with risk for glioblastoma multiforme.

Cancer risk among residents of Rhineland-Palatinate winegrowing communities: a cancer-registry based ecological study

Aim

To investigate the cancer risk among residents of Rhineland-Palatinate winegrowing communities in an ecological study.

Methods

On the basis of the Rhineland-Palatinate cancer-registry, we calculated age-adjusted incidence rate ratios for communities with a medium area under wine cultivation (>5 to 20 percent) and a large area under wine cultivation (>20 percent) in comparison with communities with a small area under wine cultivation (>0 to 5 percent). In a side analysis, standardized cancer incidence ratios (SIR) were computed separately for winegrowing communities with small, medium and large area under wine cultivation using estimated German incidence rates as reference.

Results

A statistically significant positive association with the extent of viniculture can be observed for non-melanoma skin cancer in both males and females, and additionally for prostate cancer, bladder cancer, and non-Hodgkin lymphoma in males, but not in females. Lung cancer risk is significantly reduced in communities with a large area under cultivation. In the side-analysis, elevated SIR for endocrine-related tumors of the breast, testis, prostate, and endometrium were observed.

Conclusion

This study points to a potentially increased risk of skin cancer, bladder cancer, and endocrine-mediated tumors in Rhineland-Palatinate winegrowing communities. However, due to the explorative ecologic study design and the problem of multiple testing, these findings are not conclusve for a causal relationship.

Occupational exposure to pesticides and risk of adult brain tumors

The authors examined incident glioma and meningioma risk associated with occupational exposure to insecticides and herbicides in a hospital-based, case-control study of brain cancer. Cases were 462 glioma and 195 meningioma patients diagnosed between 1994 and 1998 in three US hospitals. Controls were 765 patients admitted to the same hospitals for nonmalignant conditions. Occupational histories were collected during personal interviews. Exposure to pesticides was estimated by use of a questionnaire, combined with pesticide measurement data abstracted from published sources. Using logistic regression models, the authors found no association between insecticide and herbicide exposures and risk for glioma and meningioma. There was no association between glioma and exposure to insecticides or herbicides, in men or women. Women who reported ever using herbicides had a significantly increased risk for meningioma compared with women who never used herbicides (odds ratio = 2.4, 95% confidence interval: 1.4, 4.3), and there were significant trends of increasing risk with increasing years of herbicide exposure (p = 0.01) and increasing cumulative exposure (p = 0.01). There was no association between meningioma and herbicide or insecticide exposure among men. These findings highlight the need to go beyond job title to elucidate potential carcinogenic exposures within different occupations.

Environmental and occupational causes of cancer: new evidence 2005-2007

What do we currently know about the occupational and environmental causes of cancer? As of 2007, the International Agency for Research on Cancer (IARC) identified 415 known or suspected carcinogens. Cancer arises through an extremely complicated web of multiple causes, and we will likely never know the full range of agents or combinations of agents. We do know that preventing exposure to individual carcinogens prevents the disease. Declines in cancer rates-such as the drop in male lung cancer cases from the reduction in tobacco smoking or the drop in bladder cancer among cohorts of dye workers from the elimination of exposure to specific aromatic amines-provides evidence that preventing cancer is possible when we act on what we know. Although the overall age-adjusted cancer incidence rates in the United States among both men and women have declined in the last decade, the rates of several types of cancers are on the rise; some of which are linked to environmental and occupational exposures. This report chronicles the most recent epidemiologic evidence linking occupational and environmental exposures with cancer. Peer-reviewed scientific studies published from January 2005 to June 2007 were reviewed, supplementing our state-of-the-evidence report published in September 2005. Despite weaknesses in certain individual studies, we consider the evidence linking the increased risk of several types of cancer with specific exposures somewhat strengthened by recent publications, among them brain cancer from exposure to non-ionizing radiation, particularly radiofrequency fields emitted by mobile telephones; breast cancer from exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) before puberty; leukemia from exposure to 1,3-butadiene; lung cancer from exposure to air pollution; non-Hodgkin's lymphoma (NHL) from exposure to pesticides and solvents; and prostate cancer from exposure to pesticides, polyaromatic hydrocarbons (PAHs), and metal working fluids or mineral oils. In addition to NHL and prostate cancer, early findings from the National Institutes of Health Agricultural Health Study suggest that several additional cancers may be linked to a variety of pesticides. Our report also briefly describes the toxicological evidence related to the carcinogenic effect of specific chemicals and mechanisms that are difficult to study in humans, namely exposures to bis-phenol A and epigenetic, trans-generational effects. To underscore the multi-factorial, multi-stage nature of cancer, we also present a technical description of cancer causation summarizing current knowledge in molecular biology. We argue for a new cancer prevention paradigm, one based on an understanding that cancer is ultimately caused by multiple interacting factors rather than a paradigm based on dubious attributable fractions. This new cancer prevention paradigm demands that we limit exposure to avoidable environmental and occupational carcinogens, in combination with additional important risk factors like diet and lifestyle. The research literature related to environmental and occupational causes of cancer is constantly growing, and future updates will be carried out in light of new biological understanding of the mechanisms and new methods for studying exposures in human populations. The current state of knowledge is sufficient to compel us to act on what we know. We repeat the call of ecologist Sandra Steingraber: "From the right to know and the duty to inquire flows the obligation to act."

Environmental risk factors for brain tumors

Primary brain tumors, whether malignant or nonmalignant, have devastating consequences. Unfortunately, few known causes exist. Despite decades of epidemiologic research to identify environmental causes of brain tumors, very little progress has been made. The purpose of this paper is to review the most recent studies in the epidemiology of brain tumors. Popular topics of interest in adult brain tumor epidemiology include electromagnetic fields (particularly cellular phones), occupational exposures, nitroso-containing compounds (especially smoking), hair products, and allergic and immunologic factors. Some of these topics are also applicable to the etiology of childhood brain tumors, but additional areas of interest in the pediatric population focus on parental exposure prior to conception, maternal exposure during pregnancy, and childhood exposure to infectious agents. After an extensive review of the literature since 2001, we present the most relevant studies. Although there are many proposed associations with brain tumors, none possess the statistical significance to confidently ascribe causation. However, new findings and associations, particularly those in allergy and immunology, will present interesting opportunities for further development.

Are gliomas preventable?

Gliomas are a family of primary central nervous system tumors of variable malignancy that are derived from supporting glia (astrocytes, oligodendrocytes, ependymal cells) or their progenitors/stem cells. There are two potential strategies to prevention: preventing gliomas from forming and preventing lower-grade gliomas from developing into higher-grade gliomas. Each would lower time-dependent mortality. Each also depends on an understanding of what causes gliomas so that these factors can be modulated. In this presentation, I will discuss primary prevention, chemoprevention, and screening. I will first focus on the known chromosomal, genetic, and protein changes associated with the different histologic varieties of glioma and the environmental, hereditary, and infectious/viral factors that may promote glioma development and malignant progression. I will discuss a number of clinical scenarios that eventuate from the known genetic patterns of these tumors and the changes in genetic patterns that reflect malignant progression. The basic thinking is that if one could prevent specific gene mutations and/or deletions or gains of specific chromosomes that lead to the development of low-grade (WHO 2) gliomas, then theoretically this would reduce the occurrence of high-grade (WHO 3 and 4) gliomas and hence the almost certain death that now is the fate of most patients with these tumors. In the case of de novo WHO 3 and 4 tumors, being able to prevent or counter specific gene mutations and/or the deletion of specific chromosomes would in itself reduce the occurrence of these gliomas and increase survival. Alternatively, a curative treatment for low-grade glioma that prevents these chromosomal/gene changes would prevent some glioblastomas (WHO 4) from forming and would have the same desired effect on survival. Obviously, for the latter to be achieved, we must also be able to diagnose and treat low-grade gliomas earlier.

Gliomas and Farm Pesticide Exposure in Men: The Upper Midwest Health Study

The National Institute for Occupational Safety and Health evaluated farm pesticide exposure and glioma risk in a study that included 457 glioma cases and 648 population-based controls, all adult men (18-80 yr old) and nonmetropolitan residents of Iowa, Michigan, Minnesota, and Wisconsin. Multiple logistic regressions were used to control for farm residence, age, age group, education, and exposure to other pesticides. No associations were found between glioma and 12 specific pesticides. We estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) and found reduced glioma risk for insecticides (OR = 0.53, CI = 0.37-0.77), fumigants (OR = 0.57, CI = 0.34-0.95), and organochlorines (OR = 0.66, CI = 0.47-0.94). In analyses excluding proxy respondents (47% of cases) most CIs included 1.0. No positive association of farm pesticide exposure and glioma was found. Other farm exposures may explain the excess brain cancer risk seen in previous studies.