Helle Raun Andersen

Potential developmental neurotoxicity of pesticides used in Europe

Pesticides used in agriculture are designed to protect crops against unwanted species, such as weeds, insects, and fungus. Many compounds target the nervous system of insect pests. Because of the similarity in brain biochemistry, such pesticides may also be neurotoxic to humans. Concerns have been raised that the developing brain may be particularly vulnerable to adverse effects of neurotoxic pesticides. Current requirements for safety testing do not include developmental neurotoxicity. We therefore undertook a systematic evaluation of published evidence on neurotoxicity of pesticides in current use, with specific emphasis on risks during early development. Epidemiologic studies show associations with neurodevelopmental deficits, but mainly deal with mixed exposures to pesticides. Laboratory experimental studies using model compounds suggest that many pesticides currently used in Europe – including organophosphates, carbamates, pyrethroids, ethylenebisdithiocarbamates, and chlorophenoxy herbicides – can cause neurodevelopmental toxicity. Adverse effects on brain development can be severe and irreversible. Prevention should therefore be a public health priority. The occurrence of residues in food and other types of human exposures should be prevented with regard to the pesticide groups that are known to be neurotoxic. For other substances, given their widespread use and the unique vulnerability of the developing brain, the general lack of data on developmental neurotoxicity calls for investment in targeted research. While awaiting more definite evidence, existing uncertainties should be considered in light of the need for precautionary action to protect brain development.

Endocrine-disrupting chemicals and obesity development in humans: A review

This study reviewed the literature on the relations between exposure to chemicals with endocrine‐disrupting abilities and obesity in humans. The studies generally indicated that exposure to some of the endocrine‐disrupting chemicals was associated with an increase in body size in humans. The results depended on the type of chemical, exposure level, timing of exposure and gender. Nearly all the studies investigating dichlorodiphenyldichloroethylene (DDE) found that exposure was associated with an increase in body size, whereas the results of the studies investigating polychlorinated biphenyl (PCB) exposure were depending on dose, timing and gender. Hexachlorobenzene, polybrominated biphenyls, beta‐hexachlorocyclohexane, oxychlordane and phthalates were likewise generally associated with an increase in body size. Studies investigating polychlorinated dibenzodioxins and polychlorinated dibenzofurans found either associations with weight gain or an increase in waist circumference, or no association. The one study investigating relations with bisphenol A found no association. Studies investigating prenatal exposure indicated that exposure in utero may cause permanent physiological changes predisposing to later weight gain. The study findings suggest that some endocrine disruptors may play a role for the development of the obesity epidemic, in addition to the more commonly perceived putative contributors.

Impaired Reproductive Development in Sons of Women Occupationally Exposed to Pesticides during Pregnancy

OBJECTIVES The aim of this prospective study was to investigate whether occupational pesticide exposure during pregnancy causes adverse effects on the reproductive development in the male infants. DESIGN AND MEASUREMENTS Pregnant women employed in greenhouses in Denmark were consecutively recruited, and 113 mother-son pairs were included. The mothers were categorized as occupationally exposed (91 sons) or unexposed (22 sons) to pesticides during pregnancy. Testicular position and volume, penile length, and position of urethral opening were determined at 3 months of age using standardized techniques. Concentrations of reproductive hormones in serum from the boys were analyzed. RESULTS The prevalence of cryptorchidism at 3 months of age was 6.2% [95% confidence interval (CI), 3.0-12.4]. This prevalence was considerably higher than among Danish boys born in the Copenhagen area (1.9%; 95% CI, 1.2-3.0) examined by the same procedure. Boys of pesticide-exposed mothers showed decreased penile length, testicular volume, serum concentrations of testosterone, and inhibin B. Serum concentrations of sex hormone-binding globulin, follicle-stimulating hormone, and the luteinizing hormone:testosterone ratio were increased compared with boys of nonexposed mothers. For individual parameters, only the decreased penile length was statistically significant (p = 0.04). However, all observed effects were in the anticipated direction, and a joint multivariate test showed that this finding had a p-value of 0.012. CONCLUSIONS Our findings suggest an adverse effect of maternal occupational pesticide exposure on reproductive development in the sons despite current greenhouse safeguards and special measures to protect pregnant women.

Endocrine disrupting effects in vitro of conazole antifungals used as pesticides and pharmaceuticals.

Widely used conazole antifungals were tested for endocrine disruptive effects using a panel of in vitro assays. They all showed endocrine disrupting potential and ability to act via several different mechanisms. Overall the imidazoles (econazole, ketoconazole, miconazole, prochloraz) were more potent than the triazoles (epoxiconazole, propiconazole, tebuconazole). The critical mechanism seems to be disturbance of steroid biosynthesis. In the H295R cell assay, the conazoles decreased the formation of estradiol and testosterone, and increased the concentration of progesterone, indicating inhibition of enzymes involved in the conversion of progesterone to testosterone. Prochloraz was most potent followed by econazole~miconazole>ketoconazole>tebuconazole>epoxiconazole>propiconazole. In the MCF-7 cell proliferation assay, the conazoles showed anti-estrogenic effect, including aromatase inhibition, since they inhibited the response induced by both 17β-estradiol (miconazole>econazole~ketoconazole>prochloraz>tebuconazole>epoxiconazole>propiconazole) and testosterone (econazole>miconazole>prochloraz>ketoconazole>tebuconazole>epoxiconazole>propiconazole). The triazoles were anti-androgenic in an androgen receptor reporter gene assay (epoxiconazole∼tebuconazole>propiconazole). This effect could not be evaluated for the pharmaceutical imidazoles due to cytotoxicity.

Mixture effects of endocrine disrupting compounds in vitro

Four different equi-molar mixtures were investigated for additive endocrine disrupting effects in vitro using the concentration addition model. It was found that additive effects on the same molecular target (the androgen receptor; AR) can be predicted for both mixtures of compounds with effect on the AR (flutamide, procymidone and vinclozolin) and of compounds with and without effects on the AR [finasteride, mono-(2-ethylhexyl) phthalate, prochloraz and vinclozolin]. For a paraben mixture (methyl paraben, ethyl paraben, propyl paraben, butyl paraben and iso-butyl paraben) antagonistic effect on AR could not be predicted under assumption of additivity in our model system. For a mixture containing three azole fungicides (epoxiconazole, propiconazole and tebuconazole), the observed AR antagonistic effects were close to the predicted effect assuming additivity. Azole fungicides are known inhibitors of androgen biosynthesis and in the steroid synthesis assay using H295R cells, the inhibition of testosterone production was close to additive, whereas the inhibition of oestradiol production was over-estimated for the mixture of azole fungicides, when compared with the effect predicted when assuming additivity. Overall these and other studies show that weak endocrine disrupting compounds, like parabens and azole fungicides, give rise to combination effects when they occur in mixtures. These combination effects should be taken into account in regulatory risk assessment not to under-estimate the risks for adverse effects associated with exposure to disrupting chemicals.

Assessment of xenoestrogenic exposure by a biomarker approach: application of the E-Screen bioassay to determine estrogenic response of serum extracts

BackgroundEpidemiological documentation of endocrine disruption is complicated by imprecise exposure assessment, especially when exposures are mixed. Even if the estrogenic activity of all compounds were known, the combined effect of possible additive and/or inhibiting interaction of xenoestrogens in a biological sample may be difficult to predict from chemical analysis of single compounds alone. Thus, analysis of mixtures allows evaluation of combined effects of chemicals each present at low concentrations.MethodsWe have developed an optimized in vitro E-Screen test to assess the combined functional estrogenic response of human serum. The xenoestrogens in serum were separated from endogenous steroids and pharmaceuticals by solid-phase extraction followed by fractionation by high-performance liquid chromatography. After dissolution of the isolated fraction in ethanol-DMSO, the reconstituted extract was added with estrogen-depleted fetal calf serum to MCF-7 cells, the growth of which is stimulated by estrogen. After a 6-day incubation on a microwell plate, cell proliferation was assessed and compared with the effect of a 17-beta-estradiol standard.Results and conclusionsTo determine the applicability of this approach, we assessed the estrogenicity of serum samples from 30 pregnant and 60 non-pregnant Danish women thought to be exposed only to low levels of endocrine disruptors. We also studied 211 serum samples from pregnant Faroese women, whose marine diet included whale blubber that contain a high concentration of persistent halogenated pollutants. The estrogenicity of the serum from Danish controls exceeded the background in 22.7 % of the cases, while the same was true for 68.1 % of the Faroese samples. The increased estrogenicity response did not correlate with the lipid-based concentrations of individual suspected endocrine disruptors in the Faroese samples. When added along with the estradiol standard, an indication of an enhanced estrogenic response was found in most cases. Thus, the in vitro estrogenicity response offers a promising and feasible approach for an aggregated exposure assessment for xenoestrogens in serum.

Association between perfluorinated compounds and time to pregnancy in a prospective cohort of Danish couples attempting to conceive

BACKGROUND Perfluorinated chemicals (PFCs) have been widely used and have emerged as important food contaminants. A recent study on pregnant women suggested that PFC exposure was associated with a longer time to pregnancy (TTP). We examined the association between serum concentrations of PFCs in females and TTP in 222 Danish first-time pregnancy planners during the years 1992-1995. METHODS The couples were enrolled in the study when discontinuing birth control and followed for six menstrual cycles or until a clinically recognized pregnancy occurred. Fecundability ratio (FR) was calculated using discrete-time survival models. In addition, odds ratio (OR) for TTP >6 cycles was calculated. RESULTS OR for TTP >6 cycles for those with PFC concentrations above the median were 0.96 [95% confidence interval (CI): 0.54-1.64] for perfluorooctane sulfonic acid (PFOS), the major PFC, compared with those below the median. FRs for those with PFOS concentrations above the median were 1.05 (95% CI: 0.74-1.48) compared with those below the median. Other PFCs showed the same lack of association with TTP. The results were not affected by adjustment for covariates. PFOS and perfluorooctanoic acid concentrations were similar to those observed in a previous Danish study. CONCLUSIONS These findings suggest that exposure to PFCs affects TTP only to a small extent, if at all.

Lower birth weight and increased body fat at school age in children prenatally exposed to modern pesticides: a prospective study

BackgroundEndocrine disrupting chemicals have been hypothesized to play a role in the obesity epidemic. Long-term effects of prenatal exposure to non-persistent pesticides on body composition have so far not been investigated. The purpose of this study was to assess possible effects of prenatal exposure to currently used pesticides on childrens growth, endocrine and reproductive function.MethodsIn a prospective study of 247 children born by women working in greenhouses in early pregnancy, 168 were categorized as prenatally exposed to pesticides. At three months (n = 203) and at 6 to11 years of age (n = 177) the children underwent a clinical examination and blood sampling for analysis of IGF-I, IGFBP3 and thyroid hormones. Body fat percentage at age 6 to11 years was calculated from skin fold measurements. Pesticide related associations were tested by linear multiple regression analysis, adjusting for relevant confounders.ResultsCompared to unexposed children birth weight and weight for gestational age were lower in the highly exposed children: -173 g (-322; -23), -4.8% (-9.0; -0.7) and medium exposed children: -139 g (-272; -6), -3.6% (-7.2; -0.0). Exposed (medium and highly together) children had significantly larger increase in BMI Z-score (0.55 SD (95% CI: 0.1; 1.0) from birth to school age) and highly exposed children had 15.8% (0.2; 34.6) larger skin folds and higher body fat percentage compared to unexposed. If prenatally exposed to both pesticides and maternal smoking (any amount), the sum of four skin folds was 46.9% (95% CI: 8.1; 99.5) and body fat percentage 29.1% (95% CI: 3.0; 61.4) higher. There were subtle associations between exposure and TSH Z-score -0.66(-1.287; -0.022) and IGF-I Z-score (girls: -0.62(-1.0; -0.22), boys: 0.38(-0.03; 0.79)), but not IGFBP3.ConclusionsOccupational exposure to currently used pesticides may have adverse effects in spite of the added protection offered to pregnant women. Maternal exposure to combinations of modern, non-persistent pesticides during early pregnancy was associated with affected growth, both prenatally and postnatally. We found a biphasic association with lower weight at birth followed by increased body fat accumulation from birth to school age. We cannot rule out some residual confounding due to differences in social class, although this was adjusted for. Associations were stronger in highly exposed than in medium exposed children, and effects on body fat content at school age was potentiated by maternal smoking in pregnancy.

Paraoxonase 1 Polymorphism and Prenatal Pesticide Exposure Associated with Adverse Cardiovascular Risk Profiles at School Age

Background Prenatal environmental factors might influence the risk of developing cardiovascular disease later in life. The HDL-associated enzyme paraoxonase 1 (PON1) has anti-oxidative functions that may protect against atherosclerosis. It also hydrolyzes many substrates, including organophosphate pesticides. A common polymorphism, PON1 Q192R, affects both properties, but a potential interaction between PON1 genotype and pesticide exposure on cardiovascular risk factors has not been investigated. We explored if the PON1 Q192R genotype affects cardiovascular risk factors in school-age children prenatally exposed to pesticides. Methods Pregnant greenhouse-workers were categorized as high, medium, or not exposed to pesticides. Their children underwent a standardized examination at age 6-to-11 years, where blood pressure, skin folds, and other anthropometric parameters were measured. PON1-genotype was determined for 141 children (88 pesticide exposed and 53 unexposed). Serum was analyzed for insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 3 (IGFBP3), insulin and leptin. Body fat percentage was calculated from skin fold thicknesses. BMI results were converted to age and sex specific Z-scores. Results Prenatally pesticide exposed children carrying the PON1 192R-allele had higher abdominal circumference, body fat content, BMI Z-scores, blood pressure, and serum concentrations of leptin and IGF-I at school age than unexposed children. The effects were related to the prenatal exposure level. For children with the PON1 192QQ genotype, none of the variables was affected by prenatal pesticide exposure. Conclusion Our results indicate a gene-environment interaction between prenatal pesticide exposure and the PON1 gene. Only exposed children with the R-allele developed adverse cardiovascular risk profiles thought to be associated with the R-allele.

Early breast development in girls after prenatal exposure to non-persistent pesticides

Contemporary American and European girls experience breast development at earlier ages compared with 15-20 years ago. Alterations in BMI alone cannot account for these changes. Several currently used pesticides possess endocrine disrupting properties and may interfere with reproductive development, but human data are sparse. We examined girls whose mothers worked in greenhouses in the first trimester of pregnancy to assess the long-term effects of prenatal pesticide exposure on puberty. Mothers were prenatally categorized as exposed or unexposed to pesticides. We studied the offspring of these greenhouse workers, and evaluated the anthropometry, pubertal staging in the girls, and blood samples were drawn at 3 months of age (n = 90) and again once at school age (6-11 years, n = 83). No clinical and biochemical differences were found between the exposed and unexposed girls at 3 months of age. Mean onset of B2+ was 8.9 years (95% CI: 8.2; 9.7) in prenatally exposed girls, compared with 10.4 years (9.2; 17.6) in the unexposed (p = 0.05), and 10.0 (9.7-10.3) years in a Danish reference population (p = 0.001). Exposed girls had higher serum androstenedione levels (geometric means: 0.58 vs. 0.79 nmol/L, p = 0.046) and lower Anti-Müllerian Hormone (AMH) compared with the unexposed (geometric means: 16.4 vs. 21.3 pmol/L, p > 0.05) and the reference group (20.2 pmol/L, p = 0.012). Levels of testosterone, estradiol, prolactin, FSH, LH, SHBG, DHEAS, DHT, Inhibin A and Inhibin B did not differ between the groups. In conclusion, our findings suggest that prenatal exposure to currently approved pesticides may cause earlier breast development in girls. This association appeared not to be because of changes in gonadotropins, but rather to higher androgen levels, which indirectly may increase oestrogens through aromatization. In addition, lower serum AMH levels indicated a reduced pool of antral ovarian follicles. The long-term consequences of our findings with regard to establishment of future reproductive function still remain unknown.