Systematic review and meta-analysis of cyclodiene insecticides and breast cancer

POPs in long-finned pilot whales mass stranded in Iceland as a proxy for their physiological condition

Long-finned pilot whales (Globicephala melas) are the most frequently stranded cetaceans in the world; however, the predominant drivers of these events are poorly understood. In this study the levels of persistent organic pollutants from pilot whales stranded in North-east Iceland were quantified and compared to historical data and physical parameters to investigate whether contaminant load may have influenced the physiological state of stranded individuals, how these loads fluctuate with sex and age group, and if this is consistent with the literature. Historical comparison was also carried out to discern how pollutant contamination has changed throughout the past few decades. DDE, transnonachlor and PCB-153 were the top three pollutants respectively. The accumulation of POPs was greater on average in immature individuals than adults, whilst among adults, males had higher concentration than females. Moreover, despite an indication of decreasing POP loads throughout the years, knowledge of harmful thresholds remains exceedingly limited.

Hormonal Injustice: Environmental Toxicants as Drivers of Endocrine Health Disparities

The toll of multiple endocrine disorders has increased substantially in recent decades, and marginalized populations bear a disproportionate burden of disease. Because of the significant individual and societal impact of these conditions, it is essential to identify and address all modifiable risk factors contributing to these disparities. Abundant evidence now links endocrine dysfunction with exposure to endocrine-disrupting chemicals (EDCs), with greater exposures to multiple EDCs occurring among vulnerable groups, such as racial/ethnic minorities, those with low incomes, and others with high endocrine disease burdens. Identifying and eliminating EDC exposures is an essential step in achieving endocrine health equity.

Exposure to Organochlorine Pesticides and Female Breast Cancer Risk According to Molecular Receptors Expression: a Systematic Review and Meta-analysis of Epidemiological Evidence

PURPOSE OF REVIEW

Organochlorine pesticides (OCP) have been proposed as potential mammary carcinogens since they interact with steroid signaling pathways. However, the epidemiological results are not conclusive. Most studies have evaluated breast cancer (BC) as a single entity without considering the different molecular expressions, including estrogen receptor (ER), progesterone receptor (PR), and HER2, that could differ in their association with these contaminants. Hence, we assessed the association between biological concentration of OCP and BC, according to its molecular receptor expression, based on a systematic review and meta-analysis.

RECENT FINDINGS

Of the 141 articles eligible for full-text review, nine met the inclusion criteria. The way in which molecular expression was reported was heterogeneous; therefore, the inclusion of studies in the meta-analysis was limited to eight articles. A negative association was identified for β-hexachlorocyclohexane and trans-nonachlor with ER + tumors and between hexachlorobenzene and ER - tumors. No associations were observed for p,p'-dichlorodiphenyldichloroethylene, cis-nonachlor, and dieldrin, and it was not possible to evaluate the associations between OCP with HER2 expression or triple-negative tumors due to lack of data. The results suggest that some OCP might be associated with BC depending on the expression of ER. However, the evidence is not conclusive due to the scarce data. We identified several methodological aspects to fill the gaps in knowledge and increase the comparability among studies.

Occupational exposure to organic solvents and breast cancer risk: a systematic review and meta-analysis

Breast cancer is the most common cancer worldwide. Recent studies suggest that organic solvent exposure could be closely related to breast cancer, although the evidence remains controversial. Thus, we evaluated existing epidemiological evidence for the association between occupational solvent exposure and breast cancer. PubMed, Embase, and Cochrane Library were searched to identify published case-control and cohort studies that addressed occupational exposure to organic solvents and breast cancer, up to April, 2021. Meta-analyses using random-effects models were conducted to obtain the pooled odds ratios (OR) and 95% confidence intervals (CI) on the incidence of breast cancer in relation to occupational exposure. The pooled OR of breast cancer among workers exposed to organic solvents overall was 1.18 (95%CI, 1.11 ~ 1.25; I² = 76.3%; 24 studies), compared to those with no exposure. After stratification by menopause and study location, it was revealed that the association between occupational exposure to organic solvents and the risk of breast cancer in postmenopausal women (OR, 1.35; 95% CI, 1.09 ~ 1.67; I² = 73.4%; 7 studies) was significant, and there was also a clear association in workers in Europe (OR, 1.21; 95% CI, 1.12 ~ 1.32; I² = 82.9%; 13 studies). We observed a significant association between occupational exposure to organic solvents and breast cancer in both cohort and case-control studies.

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.

Persistent Organic Pollutants and Breast Cancer: A Systematic Review and Critical Appraisal of the Literature

Persistent organic pollutants (POPs) bioaccumulate in the food chain and have been detected in human blood and adipose tissue. Experimental studies demonstrated that POPs can cause and promote growth of breast cancer. However, inconsistent results from epidemiological studies do not support a causal relationship between POPs and breast cancer in women. To identify individual POPs that are repeatedly found to be associated with both breast cancer incidence and progression, and to demystify the observed inconsistencies between epidemiological studies, we conducted a systematic review of 95 studies retrieved from three main electronic databases. While no clear pattern of associations between blood POPs and breast cancer incidence could be drawn, POPs measured in breast adipose tissue were more clearly associated with higher breast cancer incidence. POPs were more consistently associated with worse breast cancer prognosis whether measured in blood or breast adipose tissue. In contrast, POPs measured in adipose tissue other than breast were inversely associated with both breast cancer incidence and prognosis. Differences in biological tissues used for POPs measurement and methodological biases explain the discrepancies between studies results. Some individual compounds associated with both breast cancer incidence and progression, deserve further investigation.

Pesticides and Related Toxicants in the Atmosphere

Pesticides and other toxicants released into the environment can contaminate air, water, soil, and biota. This review focuses on sources, exposures, fate, analysis, and trends. The potential for exposures due to atmospheric transport and deposition of pesticides and related contaminants may pose risks to humans and wildlife. Emissions of chemicals to air are related to physicochemical properties (e.g., vapor pressure and chemical stability). Experimental design and computer-based modeling, as related to emissions and dispersion of pesticides along transects downwind from release sources, will be discussed using the example of pesticide volatilization and drift in California agriculture that results in the transport and deposition downwind to the Sierra Nevada mountains, where much work has been done to refine exposure data for use in risk assessment and management. Predictably, those chemicals found frequently in air are those used most extensively, have multiple emission sources, and resist degradation. Yet to be determined are definitive connections with adverse impacts to humans and wildlife, although the accumulating evidence suggests that endocrine disrupting chemicals, ChE inhibitors, and others warrant further attention. Steps that are being taken to limit emissions, such as in pest control and fuel combustion, offer promising opportunities for improving the quality of air and of the overall environment. Chemical degradation rates and products from trace organics in the air merit more attention, as do the potential for activation by photooxidation and bioaccumulation in food chains. The potential effect of climate change, on atmospheric processes affecting contaminant behavior, is an area ripe for further study.

When Is Enough, Enough? When Are More Observational Epidemiologic Studies Needed to Resolve a Research Question: Illustrations Using Biomarker-Cancer Associations

BACKGROUND

Research reproducibility is vital for translation of epidemiologic findings. However, repeated studies of the same question may be undertaken without enhancing existing knowledge. To identify settings in which additional research is or is not warranted, we adapted research synthesis metrics to determine number of additional observational studies needed to change the inference from an existing meta-analysis.

METHODS

The fail-safe number (FSN) estimates number of additional studies of average weight and null effect needed to drive a statistically significant meta-analysis to null (P ≥ 0.05). We used conditional power to determine number of additional studies of average weight and equivalent heterogeneity to achieve 80% power in an updated meta-analysis to detect the observed summary estimate as statistically significant. We applied these metrics to a curated set of 98 meta-analyses on biomarkers and cancer risk.

RESULTS

Both metrics were influenced by number of studies, heterogeneity, and summary estimate size in the existing meta-analysis. For the meta-analysis on Helicobacter pylori and gastric cancer with 15 studies [OR = 2.29; 95% confidence interval (CI), 1.71-3.05], FSN was 805 studies, supporting futility of further study. For the meta-analysis on dehydroepiandrosterone sulfate and prostate cancer with 7 studies (OR = 1.29; 95% CI, 0.99-1.69), 5 more studies would be needed for 80% power, suggesting further study could change inferences.

CONCLUSIONS

Along with traditional assessments, these metrics could be used by stakeholders to decide whether additional studies addressing the same question are needed.

IMPACT

Systematic application of these metrics could lead to more judicious use of resources and acceleration from discovery to population-health impact.

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.

Association between serum persistent organic pollutants and DNA methylation in Korean adults

BACKGROUND

Exposure to persistent organic pollutants (POPs) has been associated with epigenetic changes such as DNA methylation, which can influence human health. However, the association between POPs and DNA methylation by sex was not shown in previous studies.

OBJECTIVES

We investigated the association between POPs and DNA methylation in men and women using a larger population.

METHODS

A cross-sectional study was conducted using the data of 444 Koreans (253 men and 191 women). Measurements for sixteen different POPs, including six organochlorine pesticides (OCPs) and ten polychlorinated biphenyls (PCBs) were taken in serum. DNA methylation via Alu and LINE-1 in peripheral leukocytes was measured by pyrosequencing. To evaluate the association between POPs and DNA methylation, the Pearson's correlation and multiple linear regression analyses were performed.

RESULTS

Except for PCB52 and PCB101, we found significant inverse associations between p,p'-DDE, cis-Heptachlor epoxide, and PCBs and Alu assay in men after adjusting for age, BMI, smoking status, and alcohol consumption (β = -0.67 for p,p'-DDE; -0.28 for cis-Heptachlor epoxide; in the range from -0.43 to -1.60 for PCBs). In women, PCB153 and PCB180 showed statistically significant inverse association with Alu assay (β = -0.22 for PCB153; -0.22 for PCB180). Except for PCB101, p,p'-DDE and PCBs were positively associated with LINE-1 assay in women (β = 0.48 for p,p'-DDE; in the range from 0.40-0.89 for PCBs) while p,p'-DDE, PCB153, and PCB180 showed positive associations with LINE-1 assay in men (β = 0.55 for p,p'-DDE; 0.65 for PCB153; 1.02 for PCB180).

CONCLUSIONS

We found that several POPs were associated with global DNA hypomethylation in the Alu assay for men and global DNA hypermethylation in the LINE-1 assay for women.

Insecticide Use and Breast Cancer Risk among Farmers' Wives in the Agricultural Health Study

BACKGROUND

Some epidemiologic and laboratory studies suggest that insecticides are related to increased breast cancer risk, but the evidence is inconsistent. Women engaged in agricultural work or who reside in agricultural areas may experience appreciable exposures to a wide range of insecticides.

OBJECTIVE

We examined associations between insecticide use and breast cancer incidence among wives of pesticide applicators (farmers) in the prospective Agricultural Health Study.

METHODS

Farmers and their wives provided information on insecticide use, demographics, and reproductive history at enrollment in 1993-1997 and in 5-y follow-up interviews. Cancer incidence was determined via cancer registries. Among 30,594 wives with no history of breast cancer before enrollment, we examined breast cancer risk in relation to the women's and their husbands' insecticide use using Cox proportional hazards regression to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

During an average 14.7-y follow-up, 39% of the women reported ever using insecticides, and 1,081 were diagnosed with breast cancer. Although ever use of insecticides overall was not associated with breast cancer risk, risk was elevated among women who had ever used the organophosphates chlorpyrifos [HR=1.4 (95% CI: 1.0, 2.0)] or terbufos [HR=1.5 (95% CI: 1.0, 2.1)], with nonsignificantly increased risks for coumaphos [HR=1.5 (95% CI: 0.9, 2.5)] and heptachlor [HR=1.5 (95% CI: 0.7, 2.9)]. Risk in relation to the wives' use was associated primarily with premenopausal breast cancer. We found little evidence of differential risk by tumor estrogen receptor status. Among women who did not apply pesticides, the husband's use of fonofos was associated with elevated risk, although no exposure-response trend was observed.

CONCLUSION

Use of several organophosphate insecticides was associated with elevated breast cancer risk. However, associations for the women's and husbands' use of these insecticides showed limited concordance. Ongoing cohort follow-up may help clarify the relationship, if any, between individual insecticide exposures and breast cancer risk. https://doi.org/10.1289/EHP1295.

Breast cancer and persistent organic pollutants (excluding DDT): a systematic literature review

Persistent organic pollutants (POPs) are a group of heterogeneous compounds of both natural and anthropogenic origin with highly persistent and bioaccumulative properties. They cause a range of adverse effects to human health and the environment around the world. There is growing concern that POPs may increase breast cancer risk due to their xenoestrogenic properties. The aim of this systematic literature review is to summarize and integrate the risks of breast cancer following environmental exposure to POPs (other than DDT) from primary epidemiological studies published between 2006 and 2015. After searching various databases, 14 case-control studies and one cohort study were included. Evidence of an association between increased breast cancer risk and environmental exposure to these chemicals is inconsistent and inadequate to conclude with certainty. However, most of the studies have examined exposure to the pollutants after diagnosis of breast cancer, overlooking exposure during critical windows of vulnerability. They have also largely focused on individual chemicals but ignored the combined effects of different chemicals. Therefore, major data gaps remain in examining exposure during critical windows of vulnerability and assessing combined effects of multiple chemicals. Development of better exposure assessment methods addressing these gaps is required for future research.

The integrative role of leptin, oestrogen and the insulin family in obesity-associated breast cancer: potential effects of exercise

Obesity is an established risk factor for postmenopausal breast cancer. The mechanisms through which obesity influences the development and progression of breast cancer are not fully elucidated; however, several factors such as increased oestrogen, concentrations of various members of the insulin family and inflammation that are associated with adiposity are purported to be important factors in this relationship. Emerging research has also begun to focus on the role of adipokines, (i.e. adipocyte secreted factors), in breast cancer. Leptin secretion is directly related to adiposity and is believed to promote breast cancer directly and independently, as well as through involvement with the oestrogen and insulin signalling pathways. As leptin is secreted from white adipose tissue, any intervention that reduces adiposity may be favourable. However, it is also important to consider that energy expenditure through exercise, independent of fat loss, may improve leptin regulation. The purpose of this narrative review was to explore the role of leptin in breast cancer development and progression, identify key interactions with oestrogen and the insulin family, and distinguish the potential effects of exercise on these interactions.

Application of credibility ceilings probes the robustness of meta-analyses of biomarkers and cancer risk

OBJECTIVES

Meta-analyses of biomarkers often present spurious significant results and large effects. We applied sensitivity analyses with the use of credibility ceilings to assess whether and how the results of meta-analyses of biomarkers and cancer risk would change.

STUDY DESIGN AND SETTING

We evaluated 98 meta-analyses, 43 (44%) of which had nominally statistically significant results. We assumed that any single study cannot give more than a maximum certainty 100 - c% (c, credibility ceiling) that the effect estimate [odds ratio (OR)] exceeds 1 (null) or 1.2.

RESULTS

Nominal statistical significance was maintained for 21 (21%) meta-analyses, for c = 10% and OR >1, and these proportions changed to 7%, 3%, and 6% with ceilings of 20%, 30%, and 40%, respectively. For ceilings for OR >1.2, the respective proportions were 37%, 21%, 7%, and 3%. Seven meta-analyses on infectious agents retained statistical significance even with a high ceiling of c = 20% for OR >1.00. Meta-analyses without other hints of bias (large between-study heterogeneity, small-study effects, excess significance) were more likely to retain statistical significance than those that had such hints of bias.

CONCLUSION

Credibility ceilings may be helpful in meta-analyses of biomarkers to understand the robustness of the results to different levels of uncertainty.

Plaguicidas en México: usos, riesgos y marco regulatorio

El presente documento describe la situación actual referente a la reglamentación de la producción, distribución, almacenamiento y uso de los plaguicidas en México. Se muestran datos de morbilidad como consecuencia del uso de estos productos como un referente de sus efectos sobre la salud humana, así como, los sitios en la República Mexicana en donde la incidencia es mayor. Adicionalmente, se presenta una revisión de la regulación nacional e internacional sobre plaguicidas, así como, las distintas dependencias gubernamentales, organizaciones civiles y centros de investigación involucrados en el tema en México. La información presentada sugiere que a pesar de las regulaciones y restricciones de uso de los plaguicidas, éstos pueden representar un grave problema de salud para los trabajadores y poblaciones expuestas, así como, de contaminación de suelos y aguas en México.

Evaluation of excess statistical significance in meta-analyses of 98 biomarker associations with cancer risk

BACKGROUND

Numerous biomarkers have been associated with cancer risk. We assessed whether there is evidence for excess statistical significance in results of cancer biomarker studies, suggesting biases.

METHODS

We systematically searched PubMed for meta-analyses of nongenetic biomarkers and cancer risk. The number of observed studies with statistically significant results was compared with the expected number, based on the statistical power of each study under different assumptions for the plausible effect size. We also evaluated small-study effects using asymmetry tests. All statistical tests were two-sided.

RESULTS

We included 98 meta-analyses with 847 studies. Forty-three meta-analyses (44%) found nominally statistically significant summary effects (random effects). The proportion of meta-analyses with statistically significant effects was highest for infectious agents (86%), inflammatory (67%), and insulin-like growth factor (IGF)/insulin system (52%) biomarkers. Overall, 269 (32%) individual studies observed nominally statistically significant results. A statistically significant excess of the observed over the expected number of studies with statistically significant results was seen in 20 meta-analyses. An excess of observed vs expected was observed in studies of IGF/insulin (P ≤ .04) and inflammation systems (P ≤ .02). Only 12 meta-analyses (12%) had a statistically significant summary effect size, more than 1000 case patients, and no hints of small-study effects or excess statistical significance; only four of them had large effect sizes, three of which pertained to infectious agents (Helicobacter pylori, hepatitis and human papilloma viruses).

CONCLUSIONS

Most well-documented biomarkers of cancer risk without evidence of bias pertain to infectious agents. Conversely, an excess of statistically significant findings was observed in studies of IGF/insulin and inflammation systems, suggesting reporting biases.

Endocrine-disrupting chemicals: associated disorders and mechanisms of action

The incidence and/or prevalence of health problems associated with endocrine-disruption have increased. Many chemicals have endocrine-disrupting properties, including bisphenol A, some organochlorines, polybrominated flame retardants, perfluorinated substances, alkylphenols, phthalates, pesticides, polycyclic aromatic hydrocarbons, alkylphenols, solvents, and some household products including some cleaning products, air fresheners, hair dyes, cosmetics, and sunscreens. Even some metals were shown to have endocrine-disrupting properties. Many observations suggesting that endocrine disruptors do contribute to cancer, diabetes, obesity, the metabolic syndrome, and infertility are listed in this paper. An overview is presented of mechanisms contributing to endocrine disruption. Endocrine disruptors can act through classical nuclear receptors, but also through estrogen-related receptors, membrane-bound estrogen-receptors, and interaction with targets in the cytosol resulting in activation of the Src/Ras/Erk pathway or modulation of nitric oxide. In addition, changes in metabolism of endogenous hormones, cross-talk between genomic and nongenomic pathways, cross talk with estrogen receptors after binding on other receptors, interference with feedback regulation and neuroendocrine cells, changes in DNA methylation or histone modifications, and genomic instability by interference with the spindle figure can play a role. Also it was found that effects of receptor activation can differ in function of the ligand.

Organochlorine pesticide exposure among agricultural workers in Colombian regions with illegal crops: an exploration in a hidden and dangerous world

A previous study suggested that banned organochlorine pesticides were being used to protect illegal crops from pests. The study herein explored the exposure of individuals living in a region with such crops. Samples from 99 individuals were collected during 2005 and 2006 and organochlorine pesticides were quantified using chromatography in serum samples. We detected heptachlor (72.73%), 4,4-DDE (19.19%), aldrin (15.15%), γ-chlordane (12.12%), dieldrin (11.11%), α-chlordane (10,10%), α-endosulfan (8.08%), endosulfan (6.06%), β-endosulfan (5.05%), oxychlordane (3.03%), 4,4-DDT (3.03%), and 2,4-DDT (2.02%). Heptachlor had a skewed and negative distribution (median: 8.69 ng/l and maximum: 43.8 ng/l). A two-dimensional biplot suggested that mixtures present were endosulfan/4,4-DDT, aldrin/γ-chlordane, and oxychlordane/β-endosulfan/dieldrin. We did not identify variables associated with exposure levels. These data suggest that banned organochlorine pesticides are used. This is an example of research in a war context, where the problems related with pesticides are complex, and their implications go beyond a toxicological or epidemiological viewpoint.

Phenylpyrazole insecticides induce cytotoxicity by altering mechanisms involved in cellular energy supply in the human epithelial cell model Caco-2

Phenylpyrazoles are relatively new insecticides designed to manage problematic insect resistance and public health hazards encountered with older pesticide families. In vitro cytotoxicity induced by the phenylpyrazole insecticides, Ethiprol and Fipronil, and Fipronil metabolites, sulfone and sulfide, was studied in Caco-2 cells. This cellular model was chosen because it made possible to mimic the primary site of oral exposure to xenobiotics, the intestinal epithelium. Assessment of the barrier function of Caco-2 epithelium was assessed by TEER measurement and showed a major loss of barrier integrity after exposure to Fipronil and its metabolites, but not to Ethiprol. The disruption of the epithelial barrier was attributed to severe ATP depletion independent of cell viability, as revealed by LDH release. The origin of energetic metabolism failure was investigated and revealed a transient enhancement of tetrazolium salt reduction and an increase in lactate production by Caco-2 cells, suggesting an increase in glucose metabolism by pesticides. Cellular symptoms observed in these experiments lead us to hypothesize that phenylpyrazole insecticides interacted with mitochondria.