Carcinogenicity of pentachlorophenol and some related compounds

Theoretical Study on the Reaction between Carcinogenic 2,5-Dichloro-1,4-benzoquinone and tert-Butyl Hydroperoxide: Self-Catalysis and Water Catalysis

The potentially carcinogenic halobenzoquinones (HBQs) have been recently identified in drinking water as disinfection byproducts. Several radical intermediates in the reaction of 2,5-dichloro-1,4-benzoquinone (DCBQ) and t-butyl hydroperoxide (t-BuOOH), which may induce DNA damage, were detected experimentally, and metal-independent decomposition reactions of t-BuOOH by DCBQ were proposed. It has not yet been confirmed by theoretical calculations. The theoretical study in this work provides insights into the details of the reaction. An unprecedented self-catalysis mechanism of organic hydroperoxides, that is, the reactant t-BuOOH also has a catalytic effect, was uncovered at the molecular level. Moreover, as the solvent, water molecules also clearly have an efficient catalytic effect. Due to the catalysis of t-BuOOH and water, the metal-independent reaction of t-BuOOH and DCBQ can occur under moderate conditions. Our findings about the novel catalytic effect of organic hydroperoxides t-BuOOH could offer a unique perspective into the design of new catalysts and an understanding of the catalytic biological, environmental, and air pollution reactions. Furthermore, organic hydroperoxide t-BuOOH could serve as a proton shuttle, where the proton transfer process is accompanied by simultaneous charge transfer. Therefore, organic hydroperoxides may disrupt the vital proton transfer process in biological systems and may give rise to unexpected toxicity.

Pentachlorophenol exposure induced neurotoxicity by disrupting citrulline metabolism in larvae and adult zebrafish

Pentachlorophenol (PCP) is a ubiquitous environmental toxicant with various adverse effects. Although its neurotoxicity has been reported, the underlying mechanism and subsequent detoxification remain unclear. In this study, embryos and adult zebrafish were exposed to PCP to determine its potential neurotoxic mechanism and protective indicators. The survival rate, heart rate, mobility time, active status and moving distance were significantly decreased in larvae after 30 μg/L PCP exposure. Likewise, the mobile time, latency to the first movement, velocity and moving distance of adult zebrafish were significantly reduced by PCP exposure. Untargeted metabolomics analysis of larvae revealed that arginine and proline metabolism was the primary pathway affected by PCP exposure, reflected by increased proline and decreased citrulline (CIT) contents, which were confirmed by quantitative data. PCP exposure suppressed the conversion from arginine to CIT in larvae by downregulating the expression of nos1 and nos2a. Ornithine content was increased in the brains and intestines of adult zebrafish after PCP exposure, which inhibited ornithine catabolism to CIT by downregulating otc, resulting in reduced CIT. Intriguingly, CIT supplementation significantly restored the neurobehavioral defects induced by PCP in larvae and adult zebrafish. CIT supplementation upregulated the expression of ef1α and tuba1 in larvae and inhibited the downregulation of ef1α in the brains of adult zebrafish. Taken together, these results indicated that CIT supplementation could protect against PCP-induced neurotoxicity by upregulating the expression of genes involved in neuronal development and function.

Effect of Guanine Adduct Size, Shape, and Linker Type on the Conformation of Adducted DNA: A DFT and Molecular Dynamics Study

DNA is damaged through various exogenous sources (e.g., automobile exhaust, tobacco smoke, and processed foods), which can yield diverse C8-dG bulky aryl adducts. Adducts are known to induce structural changes to DNA that can lead to various biological outcomes, ranging from cell death to diseases such as cancer. Unfortunately, the relationship between the chemical composition of the damaged product, the adducted DNA structure, and the biological consequences is not well understood, which limits the development of disease detection and prevention strategies. The present study uses density functional theory (DFT) calculations and quintuplicate 1 μs molecular dynamics (MD) simulations to characterize the structure of DNA containing 21 model C8-dG adducts that systematically differ in size (phenyl to pyrenyl), shape (α (2,3), β (3,4) fusion, or ring substitution), and nucleobase-aryl group linkage (N, O, and C-linked). DFT calculations reveal that the inherent structural features of the G nucleobase adducts are impacted by linker type and bulky moiety shape, but not size, with the conformational flexibility reducing with α-ring fusion and linker composition as N > O > C. These structural properties are maintained in nucleoside models, which also reveal an increased propensity for anti-to-syn rotation about the glycosidic bond with N < O < C linker type. Although these diverse chemical features do not influence the global structure of adducted DNA, the adducts differentially impact the conformation local to the adducted site, including the relative populations of structures with the bulky moiety in the major groove (B conformer) and intercalated (stacked) into the helix (S conformer). Specifically, while the smallest phenyl adducts favor the B conformation and the largest pyrenyl-derived adducts stabilize the S conformation, the B/S ratio decreases with an increase in ring size and N > O > C linker composition. The shape and size (length) of the adduct can further finetune the B/S ratio, with β-fused naphthyl or α-fused phenanthryl N-linked adducts and O or C-linked adducts containing ring substitution increasing the prevalence of the S adducted DNA conformation. Overall, this work uncovers the significant effect of bulky moiety size and linker type, as well as the lesser impact of aryl group shape, on adducted DNA structure, which suggests differential replication and repair outcomes, and thereby represents an important step toward rationalizing connections between the structure and biological consequences of diverse DNA adducts.

Endocrine disrupting chemicals and male fertility: from physiological to molecular effects

The deleterious effects of chemical or non-chemical endocrine disruptors (EDs) on male fertility potential is well documented but still not fully elucidated. For example, the detection of industrial chemicals' metabolites in seminal plasma and follicular fluid can affect efficiency of the gametogenesis, the maturation and competency of gametes and has guided scientists to hypothesize that endocrine disrupting chemicals (EDCs) may disrupt hormonal homoeostasis by leading to a wide range of hormonal control impairments. The effects of EDCs exposure on reproductive health are highly dependent on factors including the type of EDCs, the duration of exposure, individual susceptibility, and the presence of other co-factors. Research and scientists continue to study these complex interactions. The aim of this review is to summarize the literature to better understand the potential reproductive health risks of EDCs in France.

Protective effect of vitamin C against tetrachlorobenzoquinone-induced 5-hydroxymethylation-dependent apoptosis in HepG2 cells mainly via the mitochondrial apoptosis pathway

Tetrachlorobenzoquinone (TCBQ) is an active metabolite of pentachlorophenol, and stimulates the accumulation of ROS to trigger apoptosis. The preventive effect of vitamin C (Vc) against TCBQ-induced apoptosis in HepG2 cells is unknown. And there is little known about TCBQ-triggered 5-hydromethylcytosine (5hmC)-dependent apoptosis. Here, we confirmed that Vc alleviated TCBQ-induced apoptosis. Through investigating the underlying mechanism, we found TCBQ downregulated 5hmC levels of genomic DNA in a Tet-dependent manner, with a particularly pronounced decrease in the promoter region, using UHPLC-MS-MS analysis and hydroxymethylated DNA immunoprecipitation sequencing. Notably, TCBQ exposure resulted in alterations of 5hmC abundance to ∼91% of key genes at promoters in the mitochondrial apoptosis pathway, along with changes of mRNA expression in 87% of genes. By contrast, 5hmC abundance of genes only exhibited slight changes in the death receptor/ligand pathway. Interestingly, the pretreatment with Vc, a positive stimulator of 5hmC generation, restored 5hmC in the genomic DNA to near-normal levels. More notably, Vc pretreatment further counter-regulated TCBQ-induced alteration of 5hmC abundance in the promoter with 100% of genes, accompanying the reverse modulation of mRNA expressions in 89% of genes. These data from Vc pretreatment supported the relationship between TCBQ-induced apoptosis and the altered 5hmC abundance. Additionally, Vc also suppressed TCBQ-stimulated generation of ROS, and further increased the stability of mitochondria. Our study illuminates a new mechanism of TCBQ-induced 5hmC-dependent apoptosis, and the dual mechanisms of Vc against TCBQ-stimulated apoptosis via reversely regulating 5hmC levels and scavenging ROS. The work also provided a possible strategy for the detoxification of TCBQ.

Organochlorine pesticides and polycyclic aromatic hydrocarbons in serum of Beijing population: Exposure and health risk assessment

Organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants, but large-scale human biomonitoring and health risk assessment data on these contaminants remain limited. In this study, concentrations of 6 OCPs and 5 PAHs were determined by GC-MS/MS in 1268 human serum samples which were collected from the participants in 2017 Beijing Chronic Disease and Risk Factor Surveillance. The detection frequencies of OCPs and PAHs ranged from 64.7 % to 96.5 % and 89.4 % to 99.6 %, respectively. The most abundant contaminants in OCPs and PAHs were pentachlorophenol (PCP) and pyrene (Pyr) with median concentrations reaching up to 3.13 and 8.48 μg/L, respectively. Nonparametric tests were employed to assess the correlations among contaminants levels, demographic characteristics (age, gender, body mass index, residence) and serum biochemical indexes. Significantly higher serum levels of all PAHs were observed in suburb residents than that in urban residents (P < 0.001). Binary logistic regression analysis demonstrated that exposure to benzo(a)pyrene (OR 2.17 [1.29, 3.63]), phenanthrene (OR 1.06 [1.02, 1.11]), fluoranthene (OR 1.04 [1.02, 1.07]) and Pyr (OR 1.02 [1.01, 1.03]) might increase the occurrence of hyperglycemia, and exposure to hexachlorobenzene (HCB) (OR 1.53 [1.05, 2.22]) and pentachlorobenzene (OR 1.14 [1.02, 1.27]) were positively associated with hyperlipidemia. Furthermore, the hazard quotients (HQs) for serum HCB, PCP and p,p'-dichlorodiphenyldichloroethylene were calculated based on health-based guidance values to predict health risks. 0.2 % and 4.3 % of serum samples showed HQ values exceeding 1 for HCB and PCP, respectively, in case of the non-carcinogenic risk, while 23.1 % of HQs for HCB were above 1 in case of the carcinogenic risk for a risk level 10^-5. Our study reveals that the body burden of the Beijing general population relative to OCPs and PAHs was nonnegligible. The past exposure of HCB and PCP might adversely affect the health status of the Beijing population.

‘Teratoid’ Hepatoblastoma: An Intriguing Variant of Mixed Epithelial-Mesenchymal Hepatoblastoma

Liver neoplasms are quite rare in childhood. They often involve 6.7 cases per 10 million children aged 18 years or younger. Hepatoblastoma (HB) is the most frequent tumor, but this neoplasm’s rarity points essentially to the difficulty of performing biologic studies and large-scale therapeutic trials. On the pathological ground, HB is separated into an entirely epithelial neoplasm or a mixed neoplasm with epithelial and mesenchymal components. This last category has been further subdivided into harboring teratoid features or not. The ‘teratoid’ HB includes a mixture of components with heterologous origin. The heterologous components include neuroectoderm, endoderm, or melanin-holding cells with or without mesenchymal components. The most important criterium for the teratoid component is neuroepithelium, melanin, and, more recently, a yolk-sac-like component and neuroendocrine components. The mesenchymal components include muscle, osteoid, and cartilage, which are most often observed mainly in ‘teratoid’ neoplasms. The teratoid component or mesenchymal components are diagnosed with biopsies. They appear more prominent after chemotherapy due to the response and shrinkage of epithelial elements and non- or low-responsive components of mixed HB. This review focuses on the clinical, radiological, and pathological findings of HB with teratoid features.

Mutagenicity, health risk, and disease burden of exposure to organic micropollutants in water from a drinking water treatment plant in the Yangtze River Delta, China

A wide variety of organic micropollutants in drinking water pose a serious threat to human health. This study was aimed to reveal the characteristics of organic micropollution profiles in water from a drinking water treatment plant (DWTP) in the Yangtze River Delta, China and investigate the mutagenicity, health risk and disease burden through mixed exposure to micropollutants in water. The presence of organic micropollutants in seven categories in organic extracts (OEs) of water from the DWTP was determined, and Ames test was conducted to test the mutagenic effect of OEs. Meanwhile, health risk of exposure to organic micropollutants in finished water through three exposure routes (ingestion, dermal absorption and inhalation) was assessed with the method proposed by U.S. EPA, and disability-adjusted life years (DALYs) were combined to estimate the disease burden of cancer based on the carcinogenic risk (CR) assessment. The results showed that 28 organic micropollutants were detected in the raw and finished water at total concentrations of 967.28 ng/L and 1073.45 ng/L, respectively, of which phthalate esters (PAEs) were the dominant category (95.79% in the raw water and 96.61% in the finished water). Although the results of the Ames test for OEs were negative and the non-carcinogenic hazard index of the organic micropollutants in the finished water was less than 1 in all age groups, the total CR was 2.17 × 10^-5, higher than the negligible risk level (1.00 × 10^-6). The total DALYs caused by the organic micropollutants in the finished water was 2945.59 person-years, and the average individual DALYs was 2.21 × 10^-6 per person-year (ppy), which was 2.21 times the reference risk level (1.00 × 10^-6 ppy) defined by the WHO. Exposure to nitrosamines (NAms) was the major contributor to the total CR (92.06%) and average individual DALYs (94.58%). This study demonstrated that despite the negative result of the mutagenicity test with TA98 and TA100 strains, the health risk of exposure to organic micropollutants in drinking water should not be neglected.

Mechanistic Study on Oxidative DNA Damage and Modifications by Haloquinoid Carcinogenic Intermediates and Disinfection Byproducts

Haloquinones (XQs) are a group of carcinogenic intermediates of the haloaromatic environmental pollutants and newly identified chlorination disinfection byproducts (DBPs) in drinking water. The highly reactive hydroxyl radicals/alkoxyl radicals and quinone enoxy/ketoxy radicals were found to arise in XQs and H₂O₂ or organic hydroperoxides system, independent of transition-metal ions. However, it was not clear whether these haloquinoid carcinogens and hydroperoxides can cause oxidative DNA damage and modifications, and if so, what are the underlying molecular mechanisms. We found that 8-oxodeoxyguanosine (8-oxodG), DNA strand breaks, and three methyl oxidation products could arise when DNA was treated with tetrachloro-1,4-benzoquinone and H₂O₂ via a metal-independent and intercalation-enhanced oxidation mechanism. Similar effects were observed with other XQs, which are generally more efficient than the typical Fenton system. We further extended our studies from isolated DNA to genomic DNA in living cells. We also found that potent oxidation of DNA to the more mutagenic imidazolone dIz could be induced by XQs and organic hydroperoxides such as t-butylhydroperoxide or the physiologically relevant hydroperoxide 13S-hydroperoxy-9Z,11E-octadecadienoic acid via an unprecedented quinone-enoxy radical-mediated mechanism. These findings should provide new perspectives to explain the potential genotoxicity, mutagenesis, and carcinogenicity for the ubiquitous haloquinoid carcinogenic intermediates and DBPs.

Detecting and Quantifying Polyhaloaromatic Environmental Pollutants by Chemiluminescence-Based Analytical Method

Polyhaloaromatic compounds (XAr) are ubiquitous and recalcitrant in the environment. They are potentially carcinogenic to organisms and may induce serious risks to the ecosystem, raising increasing public concern. Therefore, it is important to detect and quantify these ubiquitous XAr in the environment, and to monitor their degradation kinetics during the treatment of these recalcitrant pollutants. We have previously found that unprecedented intrinsic chemiluminescence (CL) can be produced by a haloquinones/H₂O₂ system, a newly-found ^●OH-generating system different from the classic Fenton system. Recently, we found that the degradation of priority pollutant pentachlorophenol by the classic Fe(II)-Fenton system could produce intrinsic CL, which was mainly dependent on the generation of chloroquinone intermediates. Analogous effects were observed for all nineteen chlorophenols, other halophenols and several classes of XAr, and a novel, rapid and sensitive CL-based analytical method was developed to detect these XAr and monitor their degradation kinetics. Interestingly, for those XAr with halohydroxyl quinoid structure, a Co(II)-mediated Fenton-like system could induce a stronger CL emission and higher degradation, probably due to site-specific generation of highly-effective ^●OH. These findings may have broad chemical and environmental implications for future studies, which would be helpful for developing new analytical methods and technologies to investigate those ubiquitous XAr.

Lifetime Pesticide Use and Monoclonal Gammopathy of Undetermined Significance in a Prospective Cohort of Male Farmers

BACKGROUND

Farmers have a higher incidence of multiple myeloma, and there is suggestive evidence of an elevated prevalence of its precursor, monoclonal gammopathy of undetermined significance (MGUS), relative to the general population. Pesticide exposures are suspected to play a role; however, the biologic plausibility for associations with multiple myeloma remains unclear.

OBJECTIVES

Our objectives were to examine the prevalence of MGUS and evaluate associations with a wide range of pesticides in a large sample of farmers.

METHODS

We obtained sera and assessed MGUS among 1,638 male farmers ≥ 50  years of age in the Agricultural Health Study (AHS), a prospective cohort in Iowa and North Carolina. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed to estimate associations with MGUS for recent use (within the 12 months before phlebotomy) and cumulative intensity-weighted lifetime days of use of specific pesticides.

RESULTS

The age-standardized MGUS prevalence was significantly elevated among AHS farmers (7.7%) compared with demographically similar men in the National Health and Nutrition Examination Survey (2.8%) or Olmsted County, Minnesota (3.8%; p < 0.001 ). Recent use of permethrin was associated with MGUS [recent use vs. no recent use, OR = 1.82 (95% CI: 1.06, 3.13)], especially among those who had also used it in the past [recent and past use vs. never use, OR = 2.49 (95% CI: 1.32, 4.69)]. High intensity-weighted lifetime use of the organochlorine insecticides aldrin and dieldrin was associated with MGUS relative to those who never used either of these pesticides [OR = 2.42 (95% CI: 1.29, 4.54); p trend = 0.006 ]. We also observed a positive association with high lifetime use of petroleum oil/distillates as an herbicide, as well as an inverse association with fonofos use.

DISCUSSION

This is the largest investigation of MGUS in farmers and the first to identify an association with MGUS for permethrin, a pyrethroid insecticide previously associated with multiple myeloma. Given the continued widespread use of permethrin in various residential and commercial settings, our findings may have important implications for exposed individuals in the general population. https://doi.org/10.1289/EHP6960.

Cytotoxic aquatic pollutants and their removal by nanocomposite-based sorbents

Water is an extremely essential compound for human life and, hence, accessing drinking water is very important all over the world. Nowadays, due to the urbanization and industrialization, several noxious pollutants are discharged into water. Water pollution by various cytotoxic contaminants, e.g. heavy metal ions, drugs, pesticides, dyes, residues a drastic public health issue for human beings; hence, this topic has been receiving much attention for the specific approaches and technologies to remove hazardous contaminants from water and wastewater. In the current review, the cytotoxicity of different sorts of aquatic pollutants for mammalian is presented. In addition, we will overview the recent advances in various nanocomposite-based adsorbents and different approaches of pollutants removal from water/wastewater with several examples to provide a backdrop for future research.

Pentachlorophenol inhibits CatSper function to compromise progesterone's action on human sperm

Pentachlorophenol (PCP), a highly toxic contaminant of chlorophenols, is common in a variety of environments and presents serious risks to animal and human health. However, the reproductive toxicity and potential actions of PCP have not been investigated thoroughly, especially in humans. Here, human spermatozoa were used to evaluate the effect of PCP on cell function and to explore the underlying mechanisms. PCP had no substantive effects on sperm viability or motility, nor on the ability to penetrate viscous medium, sperm hyperactivation or spontaneous acrosome reactions. However, PCP significantly inhibited these properties induced by progesterone (P4). Consistent with the functional observations, although PCP itself did not affect the basal intracellular Ca²⁺ concentrations and CatSper current, PCP dose-dependently inhibited increases of intracellular Ca²⁺ concentrations caused by P4. In addition, the activation of CatSper induced by P4 was largely suppressed by PCP. This is the first report showing that PCP may serves as an antagonist of the P4 membrane receptor to interfere with Ca²⁺ signaling by compromising the action of P4 on regulating sperm function. These findings suggest that the reproductive toxicity of PCP should also be a matter of concern as a mammalian health risk.

Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee

The brew temperature is widely considered a key parameter affecting the final quality of coffee, with a temperature near 93 °C often described as optimal. In particular, drip brewers that do not achieve a minimum brew temperature of 92 °C within a prescribed time period fail their certification. There is little empirical evidence in terms of rigorous sensory descriptive analysis or consumer preference testing, however, to support any particular range of brew temperatures. In this study, we drip-brewed coffee to specific brew strengths, as measured by total dissolved solids (TDS), and extraction yields, as measured by percent extraction (PE), spanning the range of the classic Coffee Brewing Control Chart. Three separate brew temperatures of 87 °C, 90 °C, or 93 °C were tested, adjusting the grind size and overall brew time as necessary to achieve the target TDS and PE. Although the TDS and PE both significantly affected the sensory profile of the coffee, surprisingly the brew temperature had no appreciable impact. We conclude that brew temperature should be considered as only one of several parameters that affect the extraction dynamics, and that ultimately the sensory profile is governed by differences in TDS and PE rather than the brew temperature, at least over the range of temperatures tested.

The microorganism and biochar-augmented bioreactive top-layer soil for degradation removal of 2,4-dichlorophenol from surface runoff

Surface runoff is one of the major pollution sources impacting the quality of the surrounding waterbody. In this study, a highly-bioreactive top-layer soil incorporated with microorganism (BO) and peanut shell (PS) biochar or dairy manure (DM) biochar was proposed for removal of 2,4-dichlorophenol (2,4-DCP) from contaminated surface runoff. Both batch test and sandbox experiment consistently revealed that PS coupled with BO amendment (PS + BO) was most effective for sorption and degradation of 2,4-DCP, compared to BO and DM alone or in combination. About 77% of 6000 μg∙L^-1 2,4-DCP was absorbed within 36 h in the original low permeability bioreactive PS + BO soil layer (15 cm long×15 cm wide×4.5 cm deep) with the 0.33 L∙day^-1 processing capacity of surface runoff. Increasing the addition of quartz sand into the bioreactor soil layer by threefold the original bioreactor improved the processing capacity to 17.5 L∙day^-1. However, this permeability-optimized bioreactive layer was still not large enough to remove 2,4-DCP completely. The optimized scale by the multi-process coupling model of the convection, dispersion, adsorption, and degradation was 60 cm long × 60 cm wide × 18 cm deep where the processing capacity of 280 L·day^-1reached and 97.3% of 2,4-DCP was removed, correspondingly the 2,4-DCP concentration could meet the standard limit. In addition, the obtained model parameters showed that the biochar or microorganism significantly decreased the dispersion coefficient D of 2,4-DCP in the bioreactive layer. The 2,4-DCP distribution coefficient K_d, and first-order reaction rate λ in the PS+BO system significantly greater than that in the control, BO, and PS systems. Results from this study indicated that the top-layer soil incorporated with microorganisms and biochar is a feasible and effective approach for the surface runoff treatment.

Prediagnostic serum concentrations of organochlorine pesticides and non-Hodgkin lymphoma: A nested case-control study in the Norwegian Janus Serum Bank Cohort

BACKGROUND

Much of the marked increase in incidence of non-Hodgkin lymphoma (NHL) over the past few decades remains unexplained. Organochlorines, including organochlorine pesticides (OCPs), have been implicated as possible contributors to the increase, but the evidence is inconsistent.

OBJECTIVES

To investigate the relation between pre-diagnostic levels of OCPs and risk of NHL in a case-control study nested within the population-based Janus Serum Bank Cohort in Norway.

METHODS

Prediagnostic concentrations of 11 OCPs or OCP metabolites were measured in baseline blood samples collected between 1972 and 1978 from 190 cases and 190 controls matched on sex, county, age at blood draw, and date of blood draw. We conducted conditional logistic regression to estimate adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) for each quartile of lipid-corrected OCP/metabolite relative to the lowest quartile.

RESULTS

We observed non-significantly elevated ORs across quartiles of β-hexachlorocyclohexane compared to the lowest quartile (OR range: 1.40-1.82) although with no apparent monotonic exposure-response relationship. We also found an inverse association between risk of NHL and o,p'-DDT (OR for Q₄ vs. Q₁ = 0.44, 95% CI: 0.19, 1.01; p-trend = 0.05). In analyses stratified by age at blood collection and duration of follow-up, several other analytes, primarily chlordane-related compounds, showed inverse associations among younger participants or those with longer follow-up time between blood draw and NHL diagnosis.

CONCLUSIONS

We found only limited evidence of positive association between selected OCPs and development of NHL.

Insecticide use and risk of non-Hodgkin lymphoma subtypes: A subset meta-analysis of the North American Pooled Project

Insecticide use has been linked to increased risk of non-Hodgkin lymphoma (NHL), however, findings of epidemiologic studies have been inconsistent, particularly for NHL subtypes. We analyzed 1690 NHL cases and 5131 controls in the North American Pooled Project (NAPP) to investigate self-reported insecticide use and risk of NHL overall and by subtypes: follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL) and small lymphocytic lymphoma (SLL). Odds ratios (OR) and 95% confidence intervals for each insecticide were estimated using logistic regression. Subtype-specific associations were evaluated using ASSET (Association analysis for SubSETs). Increased risks of multiple NHL subtypes were observed for lindane (OR = 1.60, 1.20-2.10: FL, DLCBL, SLL), chlordane (OR = 1.59, 1.17-2.16: FL, SLL) and DDT (OR = 1.36, 1.06-1.73: DLBCL, SLL). Positive trends were observed, within the subsets with identified associations, for increasing categories of exposure duration for lindane (P_trend = 1.7 × 10^-4 ), chlordane (P_trend = 1.0 × 10^-3 ) and DDT (P_trend = 4.2 × 10^-3 ), however, the exposure-response relationship was nonlinear. Ever use of pyrethrum was associated with an increased risk of FL (OR = 3.65, 1.45-9.15), and the relationship with duration of use appeared monotonic (OR for >10 years: OR = 5.38, 1.75-16.53; P_trend = 3.6 × 10^-3 ). Our analysis identified several novel associations between insecticide use and specific NHL subtypes, suggesting possible etiologic heterogeneity in the context of pesticide exposure.

Potent Oxidation of DNA by Haloquinoid Disinfection Byproducts to the More Mutagenic Imidazolone dIz via an Unprecedented Haloquinone-Enoxy Radical-Mediated Mechanism

Halogenated quinones are a class of carcinogenic intermediates and newly identified chlorination disinfection byproducts in drinking water. We found recently that halogenated quinones could enhance the decomposition of hydroperoxides independent of transition-metal ions and formation of the novel quinone enoxy/ketoxy radicals. Here, we show that the major oxidation product was 2-amino-5-[(2-deoxy-β-d-erythro-pentofuranosyl)amino]-4H-imidazol-4-one (dIz) when the nucleoside 2'-deoxyguanosine (dG) was treated with tetrachloro-1,4-benzoquinone (TCBQ) and t-butyl hydroperoxide (t-BuOOH). The formation of dIz was markedly inhibited by typical radical spin-trapping agents. Interestingly and unexpectedly, we found that the generated quinone enoxy radical played a critical role in dIz formation. Using [¹⁵N₅]-8-oxodG, dIz was found to be produced either directly from dG or through the transient formation of 8-oxodG. Based on these data, we proposed that the production of dIz might be through an unusual haloquinone-enoxy radical-mediated mechanism. Analogous results were observed in the oxidation of ctDNA by TCBQ/t-BuOOH and when t-BuOOH was substituted by the endogenously generated physiologically relevant hydroperoxide 13S-hydroperoxy-9Z,11E-octadecadienoic acid. This is the first report that halogenated quinoid carcinogens and hydroperoxides can induce potent oxidation of dG to the more mutagenic product dIz via an unprecedented quinone-enoxy radical-mediated mechanism, which may partly explain their potential carcinogenicity.

Protective effect of catechin on pentachlorophenol-induced cytotoxicity and genotoxicity in isolated human blood cells

Pentachlorophenol (PCP) is an organochlorine compound that is used as pesticide, biocide, and wood preservative. PCP is highly toxic and carcinogenic. It has been detected in food and several consumable products. The toxicity of PCP is thought to be due to generation of oxidative stress in cells. We examined whether the dietary antioxidant catechin can attenuate or protect human erythrocytes and lymphocytes against PCP-induced cytotoxicity and genotoxicity, respectively. Human erythrocytes were treated with increasing concentrations of catechin (0.05-2.5 mM) for 30 min followed by addition of 0.75 mM PCP and further incubation for 4 h at 37 °C. Hemolysates were prepared and assayed for various biochemical parameters. Treatment with PCP alone increased the generation of reactive oxygen and nitrogen species, lipid and protein oxidation, and damaged the plasma membrane, when compared to PCP untreated (control) cells. It significantly decreased glutathione level, total sulfhydryl content, and cellular antioxidant power. PCP treatment lowered the activity of antioxidant enzymes and inhibited enzymes of glucose metabolism. However, prior incubation with catechin attenuated the PCP-induced changes in all these parameters in a catechin concentration-dependent manner. Scanning electron microscopy of erythrocytes confirmed these biochemical results. PCP treatment converted the normal discoidal erythrocytes to irregularly contracted cells, acanthocytes, and echinocytes but the presence of catechin inhibited these morphological changes and erythrocytes retained their biconcave shape to a large extent. Genotoxicity was studied in human lymphocytes by single-cell gel electrophoresis (comet assay). It showed strand breaks and longer comet tail length in PCP alone treated cells. The comet tail length was reduced in the catechin +PCP-treated lymphocytes showing that catechin protected cells from PCP-induced DNA damage. These results show that catechin protects human blood cells against PCP-induced oxidative damage.

An unexpected antioxidant and redox activity for the classic copper-chelating drug penicillamine

Penicillamine has been widely-used clinically as a copper-chelating drug for the treatment of copper-overload in Wilson's disease. In this study, we found that penicillamine provided marked protection against cytotoxicity induced by tetrachlorohydroquinone (TCHQ), a major toxic metabolite of the well-known wood preservative pentachlorophenol, while other classic copper-chelating agents do not. We found, unexpectedly, that both TCHQ autooxidation and tetrachlorosemiquinone radical (TCSQ^•-) formation were remarkably delayed by penicillamine. Further investigation showed that TCSQ^•- was reduced back to TCHQ by penicillamine, with the concurrent formation of its corresponding disulfide. These data demonstrated that the protection by penicillamine against TCHQ-induced toxicity was not due to its classic Cu-chelating property, but rather to its reduction of the reactive TCSQ^•- to the much less-reactive TCHQ. This is the first report of an unexpected antioxidant and redox activity for penicillamine, which might prove highly relevant to its biological activities.

Prediagnostic blood levels of organochlorines and risk of non-Hodgkin lymphoma in three prospective cohorts in China and Singapore

Specific organochlorines (OCs) have been associated with non-Hodgkin lymphoma (NHL) with varying degrees of evidence. These associations have not been evaluated in Asia, where the high exposure and historical environmental contamination of certain OC pesticides (e.g., dichlorodiphenyltrichloroethane [DDT], hexachlorocyclohexane [HCH]) are different from Western populations. We evaluated NHL risk and prediagnostic blood levels of OC pesticides/metabolites and polychlorinated biphenyl congeners in a case-control study of 167 NHL cases and 167 controls nested within three prospective cohorts in Shanghai and Singapore. Conditional logistic regression was used to analyze lipid-adjusted OC levels and NHL risk. Median levels of p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), the primary DDT metabolite, and β-HCH were up to 12 and 65 times higher, respectively, in samples from the Asian cohorts compared to several cohorts in the United States and Norway. An increased risk of NHL was observed among those with higher β-HCH levels both overall (3rd vs. 1st tertile OR = 1.8, 95%CI = 1.0-3.2; ptrend = 0.049) and after excluding cases diagnosed within 2 years of blood collection (3rd vs. 1st tertile OR = 2.0, 95%CI = 1.1-3.9; ptrend = 0.03), and the association was highly consistent across the three cohorts. No significant associations were observed for other OCs, including p,p'-DDE. Our findings provide support for an association between β-HCH blood levels and NHL risk. This is a concern because substantial quantities of persistent, toxic residues of HCH are present in the environment worldwide. Although there is some evidence that DDT is associated with NHL, our findings for p,p'-DDE do not support an association.

An unexpected new pathway for nitroxide radical production via more reactve nitrogen-centered amidyl radical intermediate during detoxification of the carcinogenic halogenated quinones by N-alkyl hydroxamic acids

We found previously that nitroxide radical of desferrioxamine (DFO^•) could be produced from the interaction between the classic iron chelating agent desferrioxamine (DFO, an N-alkyl trihydroxamic acid) and tetrachlorohydroquinone (TCHQ), one of the carconogenic quinoind metabolites of the widely used wood preservative pentachlorophenol. However, the underlying molecular mechanism remains unclear. Here N-methylacetohydroxamic acid (N-MeAHA) was synthesized and used as a simple model compound of DFO for further mechanistic study. As expected, direct ESR studies showed that nitroxide radical of N-MeAHA (Ac-(CH₃)NO^•) can be produced from N-MeAHA/TCHQ. Interestingly and unexpectedly, when TCHQ was substituted by its oxidation product tetrachloro-1,4-benzoquinone (TCBQ), although Ac-(CH₃)NO^• could also be produced, no concurrent formation of tetrachlorosemiquinone radical (TCSQ^•) and TCHQ was detected, suggesting that Ac-(CH₃)NO^• did not result from direct oxidation of N-MeAHA by TCSQ^• or TCBQ as proposed previously. To our surprise, a new nitrogen-centered amidyl radical was found to be generated from N-MeAHA/TCBQ, which was observed by ESR with the spin-trapping agents and further unequivacally identified as Ac-(CH₃)N^• by HPLC-MS. The final product of amidyl radical was isolated and identified as its corresponding amine. Analogous radical homolysis mechanism was observed with other halogenated quinoid compounds and N-alkyl hydroxamic acids including DFO. Interestingly, amidyl radicals were found to induce both DNA strand breaks and DNA adduct formation, suggesting that N-alkyl hydroxamic acids may exert their potential side-toxic effects via forming the reactive amidyl radical species. This study represents the first report of an unexpected new pathway for nitroxide radical production via hydrogen abstration reaction of a more reactive amidyl radical intermediate during the detoxification of the carcinogenic polyhalogenated quinones by N-alkyl hydroxamic acids, which provides more direct experimental evidence to better explain not only our previous finding that excess DFO can provide effective but only partial protection against TCHQ (or TCBQ)-induced biological damage, and also the potential side-toxic effects induced by DFO and other N-alkyl hydroxamic acid drugs.

Pesticide use and risk of non-Hodgkin lymphoid malignancies in agricultural cohorts from France, Norway and the USA: a pooled analysis from the AGRICOH consortium

BACKGROUND

Pesticides are commonly used in agriculture, and previous studies endorsed the need to further investigate the possible association between their use and risk of lymphoid malignancies in agricultural workers.

METHODS

We investigated the relationship of ever use of 14 selected pesticide chemical groups and 33 individual active chemical ingredients with non-Hodgkin lymphoid malignancies (NHL) overall or major subtypes, in a pooled analysis of three large agricultural worker cohorts. Pesticide use was derived from self-reported history of crops cultivated combined with crop-exposure matrices (France and Norway) or self-reported lifetime use of active ingredients (USA). Cox regression models were used to estimate cohort-specific hazard ratios (HRs) and 95% confidence intervals (CIs), which were combined using random effects meta-analysis to calculate meta-HRs.

RESULTS

During follow-up, 2430 NHL cases were diagnosed in 316 270 farmers accruing 3 574 815 person-years under risk. Most meta-HRs suggested no association. Moderately elevated meta-HRs were seen for: NHL and ever use of terbufos (meta-HR = 1.18, 95% CI: 1.00-1.39); chronic lymphocytic leukaemia/small lymphocytic lymphoma and deltamethrin (1.48, 1.06-2.07); and diffuse large B-cell lymphoma and glyphosate (1.36, 1.00-1.85); as well as inverse associations of NHL with the broader groups of organochlorine insecticides (0.86, 0.74-0.99) and phenoxy herbicides (0.81, 0.67-0.98), but not with active ingredients within these groups, after adjusting for exposure to other pesticides.

CONCLUSIONS

Associations of pesticides with NHL appear to be subtype- and chemical-specific. Non-differential exposure misclassification was an important limitation, showing the need for refinement of exposure estimates and exposure-response analyses.

Pre-diagnostic serum concentrations of organochlorines and risk of acute myeloid leukemia: A nested case-control study in the Norwegian Janus Serum Bank Cohort

BACKGROUND

Epidemiologic studies suggest an increased risk of leukemia among individuals occupationally exposed to some organochlorine (OC) compounds. Associations between serum OC pesticide and polychlorinated biphenyl (PCB) levels and risk of acute myeloid leukemia (AML), the most common subtype of acute leukemia in adult populations, have not been evaluated prospectively in the general population.

OBJECTIVE

We evaluated the risk of AML in relation to pre-diagnostic serum levels of OC pesticides and PCBs in a case-control study nested within the Janus Serum Bank Cohort.

METHODS

Janus is a large population-based cohort containing biologic samples collected beginning in the early 1970s from ~318,000 individuals in Norway. Serum levels of 11 OC pesticides or their metabolites and 34 PCB congeners were measured in 56 AML cases and 288 controls. Conditional logistic regression was conducted to evaluate associations between lipid-adjusted serum OC levels and risk of AML.

RESULTS

Higher serum levels of total chlordane/heptachlor metabolites were associated with AML risk (3rd vs. 1st tertile odds ratio (OR) = 2.26, 95% confidence interval (CI) = 0.91-5.63; p_trend = 0.11). Significant exposure-response associations were observed for levels of heptachlor epoxide (3rd vs. 1st tertile OR = 2.85, 95% CI = 1.05-7.73; p_trend = 0.02) and dieldrin (3rd vs. 1st tertile OR = 2.71, 95% CI = 1.07-6.83; p_trend = 0.03). No significant exposure-response associations with AML risk were observed for total DDT or individual isomers and derivatives. Higher serum levels of p,p'-DDT showed a non-significant increase in risk, but the exposure-response became attenuated when co-adjusting for heptachlor epoxide or dieldrin levels. Serum PCB levels were not significantly associated with AML risk.

CONCLUSIONS

Our data suggest that higher serum levels of dieldrin and metabolites derived from chlordane/heptachlor are associated with risk of AML in the general Norwegian population, based on samples collected on average ~17 years before diagnosis. Further research in populations with historically high or recent exposure to DDT is warranted to assess the association with AML risk with body burden of specific DDT isomers and derivatives.

An unusual double radical homolysis mechanism for the unexpected activation of the aldoxime nerve-agent antidotes by polyhalogenated quinoid carcinogens under normal physiological conditions

We have recently shown that the pyridinium aldoximes, best-known as therapeutic antidotes for chemical warfare nerve-agents, could markedly detoxify the carcinogenic tetrachloro-1,4-benzoquinone (TCBQ) via an unusual double Beckmann fragmentation mechanism. However, it is still not clear why pralidoxime (2-PAM) cannot provide full protection against TCBQ-induced biological damages even when 2-PAM was in excess. Here we show, unexpectedly, that TCBQ can also activate pralidoxime to generate a reactive iminyl radical intermediate in two-consecutive steps, which was detected and unequivocally characterized by the complementary application of ESR spin-trapping, HPLC/MS and nitrogen-15 isotope-labeling studies. The same iminyl radical was observed when TCBQ was substituted by other halogenated quinones. The end product of iminyl radical was isolated and identified as its corresponding reactive and toxic aldehyde. Based on these data, we proposed that the reaction of 2-PAM and TCBQ might be through the following two competing pathways: a nucleophilic attack of 2-PAM on TCBQ forms an unstable transient intermediate, which can decompose not only heterolytically to form 2-CMP via double Beckmann fragmentation, but also homolytically leading to the formation of a reactive iminyl radical in double-steps, which then via H abstraction and further hydrolyzation to form its corresponding more toxic aldehyde. Analogous radical homolysis mechanism was observed with other halogenated quinones and pyridinium aldoximes. This study represents the first detection and identification of reactive iminyl radical intermediates produced under normal physiological conditions, which provides direct experimental evidence to explain only the partial protection by 2-PAM against TCBQ-induced biological damages, and also the potential side-toxic effects induced by 2-PAM and other pyridinium aldoxime nerve-agent antidotes.

Increased exposure to pesticides and colon cancer: Early evidence in Brazil

Environmental factors may increase colon cancer (CC) risk. It has been suggested that pesticides could play a significant role in the etiology of this malignancy. As agriculture is one of the mainstays of the Brazilian economy, this country has become the largest pesticides consumer worldwide. The CC burden is also increasing in Brazil. Herein, we examined data from the Brazilian Federal Government to determine whether CC mortality and pesticide consumption may be associated. Database of the Ministry of Health provided CC mortality data in Brazil, while pesticide usage was accessed at the website of Brazilian Institute of Environment and Renewable Natural Resources. The CC mortality in the Brazilian states was calculated as standard mortality rates (SMR). All Bayesian analysis was performed using a Markov chain Monte Carlo method in WinBUGS software. We observed that CC mortality has exhibited a steady increase for more than a decade, which correlated with the amount of sold pesticides in the country. Both observations are concentrated in the Southern and the Southeast regions of Brazil. Although ecological studies like ours have methodological limitations, the current dataset suggests the possibility that pesticide exposure may be a risk factor for CC. It warrants further investigation.

Organochlorine concentrations in adipose tissue and survival in postmenopausal, Danish breast cancer patients

BACKGROUND

Several studies have investigated an association between organochlorine-concentrations and breast cancer incidence, whereas few have investigated an association with breast cancer mortality.

METHODS

We used Cox Proportional Hazards Models to estimate the association between adipose organochlorine-concentrations and mortality after breast cancer in a survivor-cohort of 399 postmenopausal women. During a median follow-up of 16.1 years, 177 women died; 119 from breast cancer.

RESULTS

There was a general inverse association with PCB-concentration (e.g. ΣPCBs: Mortality Rate Ratio (MRR) 0.79, 95% confidence interval (CI) (0.64-0.98) per inter-quartile range (IQR)), and for all pesticides, except β-Hexachlorocyclohexane, which was not associated with mortality (MRR 1.02(0.87-1.18) per IQR), and dieldrin, which was associated with a significantly increased risk of death (MRR 1.22(1.05-1.41) per IQR). We found an interaction with prognostic factors for all PCBs, confining the inverse association to those with adverse prognostic factors. Results for pesticides suggested a similar, but mostly non-significant interaction. Dieldrin diverged from the general picture by being associated with increased mortality across all strata.

CONCLUSION

A higher concentration of PCBs and several organochlorine pesticides may be inversely associated with breast cancer mortality among women with adverse prognostic factors. Further studies are required to investigate if this is a causal association. Dieldrin was associated with a higher mortality, regardless of prognostic factors.

IMPACT

This is the first study to investigate an association between organochlorine concentrations in adipose tissue and breast cancer mortality. A prominent finding is a strong interaction with prognostic factors. The unexpected direction of association for most organochlorines encourages further studies of the role of individual metabolism of the organochlorines and a potentially stronger effect of the metabolites on mortality.

Application of the key characteristics of carcinogens in cancer hazard identification

Smith et al. (Env. Health Perspect. 124: 713, 2016) identified 10 key characteristics (KCs), one or more of which are commonly exhibited by established human carcinogens. The KCs reflect the properties of a cancer-causing agent, such as 'is genotoxic,' 'is immunosuppressive' or 'modulates receptor-mediated effects,' and are distinct from the hallmarks of cancer, which are the properties of tumors. To assess feasibility and limitations of applying the KCs to diverse agents, methods and results of mechanistic data evaluations were compiled from eight recent IARC Monograph meetings. A systematic search, screening and evaluation procedure identified a broad literature encompassing multiple KCs for most (12/16) IARC Group 1 or 2A carcinogens identified in these meetings. Five carcinogens are genotoxic and induce oxidative stress, of which pentachlorophenol, hydrazine and malathion also showed additional KCs. Four others, including welding fumes, are immunosuppressive. The overall evaluation was upgraded to Group 2A based on mechanistic data for only two agents, tetrabromobisphenol A and tetrachloroazobenzene. Both carcinogens modulate receptor-mediated effects in combination with other KCs. Fewer studies were identified for Group 2B or 3 agents, with the vast majority (17/18) showing only one or no KCs. Thus, an objective approach to identify and evaluate mechanistic studies pertinent to cancer revealed strong evidence for multiple KCs for most Group 1 or 2A carcinogens but also identified opportunities for improvement. Further development and mapping of toxicological and biomarker endpoints and pathways relevant to the KCs can advance the systematic search and evaluation of mechanistic data in carcinogen hazard identification.

Typical Soil Redox Processes in Pentachlorophenol Polluted Soil Following Biochar Addition

Reductive dechlorination is the primary pathway for environmental removal of pentachlorophenol (PCP) in soil under anaerobic condition. This process has been verified to be coupled with other soil redox processes of typical biogenic elements such as carbon, iron and sulfur. Meanwhile, biochar has received increasing interest in its potential for remediation of contaminated soil, with the effect seldom investigated under anaerobic environment. In this study, a 120-day anaerobic incubation experiment was conducted to investigate the effects of biochar on soil redox processes and thereby the reductive dechlorination of PCP under anaerobic condition. Biochar addition (1%, w/w) enhanced the dissimilatory iron reduction and sulfate reduction while simultaneously decreased the PCP reduction significantly. Instead, the production of methane was not affected by biochar. Interestingly, however, PCP reduction was promoted by biochar when microbial sulfate reduction was suppressed by addition of typical inhibitor molybdate. Together with Illumina sequencing data regarding analysis of soil bacteria and archaea responses, our results suggest that under anaerobic condition, the main competition mechanisms of these typical soil redox processes on the reductive dechlorination of PCP may be different in the presence of biochar. In particularly, the effect of biochar on sulfate reduction process is mainly through promoting the growth of sulfate reducer (Desulfobulbaceae and Desulfobacteraceae) but not as an electron shuttle. With the supplementary addition of molybdate, biochar application is suggested as an improved strategy for a better remediation results by coordinating the interaction between dechlorination and its coupled soil redox processes, with minimum production of toxic sulfur reducing substances and relatively small emission of greenhouse gas (CH4) while maximum removal of PCP.

Environmental chemicals and breast cancer: An updated review of epidemiological literature informed by biological mechanisms

BACKGROUND

Many common environmental chemicals are mammary gland carcinogens in animal studies, activate relevant hormonal pathways, or enhance mammary gland susceptibility to carcinogenesis. Breast cancer's long latency and multifactorial etiology make evaluation of these chemicals in humans challenging.

OBJECTIVE

For chemicals previously identified as mammary gland toxicants, we evaluated epidemiologic studies published since our 2007 review. We assessed whether study designs captured relevant exposures and disease features suggested by toxicological and biological evidence of genotoxicity, endocrine disruption, tumor promotion, or disruption of mammary gland development.

METHODS

We systematically searched the PubMed database for articles with breast cancer outcomes published in 2006-2016 using terms for 134 environmental chemicals, sources, or biomarkers of exposure. We critically reviewed the articles.

RESULTS

We identified 158 articles. Consistent with experimental evidence, a few key studies suggested higher risk for exposures during breast development to dichlorodiphenyltrichloroethane (DDT), dioxins, perfluorooctane-sulfonamide (PFOSA), and air pollution (risk estimates ranged from 2.14 to 5.0), and for occupational exposure to solvents and other mammary carcinogens, such as gasoline components (risk estimates ranged from 1.42 to 3.31). Notably, one 50-year cohort study captured exposure to DDT during several critical windows for breast development (in utero, adolescence, pregnancy) and when this chemical was still in use. Most other studies did not assess exposure during a biologically relevant window or specify the timing of exposure. Few studies considered genetic variation, but the Long Island Breast Cancer Study Project reported higher breast cancer risk for polycyclic aromatic hydrocarbons (PAHs) in women with certain genetic variations, especially in DNA repair genes.

CONCLUSIONS

New studies that targeted toxicologically relevant chemicals and captured biological hypotheses about genetic variants or windows of breast susceptibility added to evidence of links between environmental chemicals and breast cancer. However, many biologically relevant chemicals, including current-use consumer product chemicals, have not been adequately studied in humans. Studies are challenged to reconstruct exposures that occurred decades before diagnosis or access biological samples stored that long. Other problems include measuring rapidly metabolized chemicals and evaluating exposure to mixtures.

A Perspective Discussion on Rising Pesticide Levels and Colon Cancer Burden in Brazil

Agriculture is a mainstay of many developing countries’ economy, such as Brazil. According to the Food and Agriculture Organization of the United Nations, Brazil is the major global consumer of pesticides. Irrespective of the fact that the International Agency for Research on Cancer suggests that pesticides promote human cancer risk, a prospective study reports that colorectal cancer (CRC) burden will increase in developing countries by approximately 60% in the coming decades. Here, we review the literature and public data from the Brazilian Federal Government to explore why pesticides levels and new cases of colon cancer (CC) are rising rapidly in the country. CC incidence is the second most common malignancy in men and women in the South and the Southeast of Brazil. However, while these regions have almost doubled their pesticide levels and CC mortality in 14 years, the amount of sold pesticides increased 5.2-fold with a corresponding 6.2-fold increase in CC mortality in Northern and Northeastern states. Interestingly, mortality from endocrine, nutritional, and metabolic diseases are rapidly increasing, in close resemblance with the pesticide detection levels in food. Taken together, we discuss the possibility that pesticides might alter the risk of CC.

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.

Use of high-throughput in vitro toxicity screening data in cancer hazard evaluations by IARC Monograph Working Groups

Evidence regarding carcinogenic mechanisms serves a critical role in International Agency for Research on Cancer (IARC) Monograph evaluations. Three recent IARC Working Groups pioneered inclusion of the US Environmental Protection Agency (EPA) ToxCast program high-throughput screening (HTS) data to supplement other mechanistic evidence. In Monograph V110, HTS profiles were compared between perfluorooctanoic acid (PFOA) and prototypical activators across multiple nuclear receptors. For Monograph V112-113, HTS assays were mapped to 10 key characteristics of carcinogens identified by an IARC expert group, and systematically considered as an additional mechanistic data stream. Both individual assay results and ToxPi-based rankings informed mechanistic evaluations. Activation of multiple nuclear receptors in HTS assays showed that PFOA targets not only peroxisome proliferator activated receptors, but also other receptors. ToxCast assays substantially covered 5 of 10 key characteristics, corroborating literature evidence of "induces oxidative stress" and "alters cell proliferation, cell death or nutrient supply" and filling gaps for "modulates receptor-mediated effects." Thus, ToxCast HTS data were useful both in evaluating specific mechanistic hypotheses and in contributing to the overall evaluation of mechanistic evidence. However, additional HTS assays are needed to provide more comprehensive coverage of the 10 key characteristics of carcinogens that form the basis of current IARC mechanistic evaluations.