Prenatal exposure to pesticides: a feasibility study among migrant and seasonal farmworkers

Prenatal exposure to the herbicide 2,4-D is associated with deficits in auditory processing during infancy

INTRODUCTION

Despite widespread use, many herbicides and fungicides are not well studied for neurological effects. Fetal and infant brains are rapidly developing, yet the effects of early-life exposure to these classes of pesticides on visual and auditory function are unknown. Here we examined the effects of prenatal herbicide and fungicide exposure on infant grating visual acuity (VA) and auditory brainstem response (ABR).

METHODS

9 herbicides and 13 fungicides were measured in umbilical cord blood plasma from a cohort of infants in Fuyang County, China (n = 232). Grating VA and ABR latencies for waves I, III, V were measured at 3 time points: 6 weeks, 9 months, and 18 months. Outcomes included VA score, ABR wave V latency and ABR central conduction time (CCT [wave V- wave I]). Pesticides were analyzed as 3-level ordinal (non-detect [ND]/medium/high), or dichotomous (ND/detect), depending on detection rates. Linear mixed models were used to evaluate relations between pesticides and VA and ABR outcomes.

RESULTS

2,4-dichloroacetic acid (2,4-D), prometryn, simazine, and tetrahydrophthalamide (THPI, a metabolite of captan) were detected in 27%, 81%, 17%, and 16% of samples, respectively. Infants prenatally exposed to 2,4-D had slower auditory response times at 6 weeks. Infants with cord levels of 2,4-D > 1.17 ng/mL had wave V latencies that were 0.12 (95% CI: 0.03, 0.22) ms slower (p = 0.01) and overall CCTs that were 0.15 (95% CI:0.05, 0.25) ms slower (p = 0.003) than infants with non-detectable 2,4-D in their cord blood. No other statistically significant findings were observed for the other herbicides and fungicides or for the grating VA outcome.

CONCLUSIONS

Prenatal exposure to the herbicide 2,4-D was associated with slower auditory signal transmission in early infancy. ABR latencies reflect auditory pathway maturation and longer latencies may indicate delayed auditory development.

Potential impact of the herbicide 2,4-dichlorophenoxyacetic acid on human and ecosystems

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is applied directly to aquatic and conventional farming systems to control weeds, and is among the most widely distributed pollutants in the environment. Non-target organisms are exposed to 2,4-D via several ways, which could produce toxic effects depending on the dose, frequency of exposure, and the host factors that influence susceptibility and sensitivity. An increasing number of experimental evidences have shown concerns about its presence/detection in the environment, because several investigations have pointed out its potential lethal effects on non-target organisms. In this review, we critically evaluated the environmental fate and behavior of 2,4-D along with its eco-toxicological effects on aquatic, plants and human life to provide concise assessment in the light of recently published reports. The findings demonstrate that 2,4-D is present in a low concentration in surface water of regions where its usage is high. The highest concentrations of 2,4-D were detected in soil, air and surface water surrounded by crop fields, which suggest that mitigation strategies must be implanted locally to prevent the entry of 2,4-D into the environment. A general public may have frequent exposure to 2,4-D due to its wide applications at home lawns and public parks, etc. Various in vivo and in vitro investigations suggest that several species (or their organs) at different trophic levels are extremely sensitive to the 2,4-D exposure, which may explain variation in outcomes of reported investigations. However, implications for the prenatal exposure to 2,4-D remain unknown because 2,4-D-induced toxicity thresholds in organism have only been derived from juveniles or adults. In near future, introduction of 2,4-D resistant crops will increase its use in agriculture, which may cause relatively high and potentially unsafe residue levels in the environment. The recent findings indicate the urgent need to further explore fate, accumulation and its continuous low level exposure impacts on the environment to generate reliable database which is key in drafting new regulation and policies to protect the population from further exposure.

Developmental toxicity of 2,4-dichlorophenoxyacetic acid in zebrafish embryos

2,4-Dichlorophenoxyacetic acid (2,4-D) is widely used in agriculture as herbicide/pesticide, plant growth regulator and fruit preservative agent. It progressively accumulates in the environment including surface water, air and soil. It could be detected in human food and urine, which poses great risk to the living organisms. In the present study, we investigated the developmental toxicity of 2,4-D on zebrafish (Danio rerio) embryo. 2,4-D exposure significantly decreased both the survival rate (LC₅₀ = 46.71 mg/L) and hatching rate (IC₅₀ = 46.26 mg/L) of zebrafish embryos. The most common developmental defect in 2,4-D treated embryos was pericardial edema. 2,4-D (25 mg/L) upregulated marker genes of cardiac development (vmhc, amhc, hand2, vegf, and gata1) and downregulated marker genes of oxidative stress (cat and gpx1a). Whole mount in situ hybridization confirmed the vmhc and amhc upregulation by 2,4-D treatment. LC/MS/MS showed that the bioaccumulation of 2,4-D in zebrafish embryos were increased in a time-dependent manner after 25 mg/L of 2,4-D treatment. Taken together, our study investigated the toxic effects of 2,4-D on zebrafish embryonic development and its potential molecular mechanisms, gave evidence for the full understanding of 2,4-D toxicity on living organisms and shed light on its environmental impact.

Human health risks associated with residual pesticide levels in edible tissues of slaughtered cattle in Benin City, Southern Nigeria

Pesticide residues in meat is of growing concern due to possible adverse effects on humans. Pesticide levels were assessed in five edible cattle parts: muscle, liver, kidney and tongue tissues to determine human health risk associated with consumption of these tissues. Health risk estimates were analysed using estimated daily intake (EDI), hazard quotient (HQ) and hazard index (HI) for two (2) age/weight categories: 1-11years/30 kg for children while 70 kg was used for adult. Risks were categorized for non-carcinogenic and carcinogenic health effects and measured at the average, maximum, 50th and 95th percentiles of the measured exposure concentrations (MEC). Total pesticide residues ranged from 2.38 to 3.86 μg/kg (muscle), 3.58 to 6.3 μg/kg (liver), 1.87 to 4.59 μg/kg (kidney) and 2.54 to 4.35 μg/kg (tongue). Residual pesticide concentrations in the tissues were in the order: Liver > Tongue > Muscle > Kidney. The concentrations of all the assessed pesticides observed in the tissues were however lower than the recommended maximum residual limits (MRLs). Human health risk estimations for the children showed EDI values for heptachlor epoxide, aldrin and dieldrin exceeding threshold values. Non-cancer risk posed to children on consumption of contaminated cattle parts showed HQ values for heptachlor epoxide, aldrin, dieldrin and HI values for organochlorines exceeding 1, indicating the possibility of non-carcinogenic health risks to consumers especially children from consumption of cattle meat from the selected abattoirs.

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

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

Assessing levels of contaminants in breast milk: methodological issues and a framework for future research

To assess the scale of the possible exposure by the breast-fed infant to potentially harmful substances in breast milk, methodologically robust studies are essential. Many studies in this field, however, do not report details of crucial issues such as recruitment and milk sampling. The aims of the study reported here were to develop robust methods for the study of contaminants in breast milk, and to develop a framework for future research and population monitoring. Three cohorts of women and babies were recruited by midwives from five sites in northern England. Cohort 1 (cross-sectional, n = 322) were asked to provide two milk samples, one at one week following birth and one at a subsequent time point. Cohort 2 (longitudinal, n = 54) were asked to provide five samples at specified time points over the first 12-16 weeks after birth. Cohort 3 (convenience, n = 18), mothers of babies in the Special Care Unit, were asked to donate surplus breast milk. A novel method of analysing fat concentration in small volumes was developed and tested. A randomly selected set of samples from different donors and stages of lactation was screened for organochlorine pesticide residues, polychlorinated biphenyls, dioxins/furans, phthalates and heavy metals. A total of 453 samples were donated. Cohort 3 was the least successful route of recruitment. Cohorts 1 and 2 combined were most representative of the population. Sample collection, transport and storage procedures, and the collection of data on life style and diet, were robust and acceptable to women. Midwifery involvement in recruitment was an essential component. This study offers a framework both for the conduct of future research studies, and for the establishment of regional and national monitoring mechanisms for contaminants in breast milk. Similar work on contaminants in formula as fed to babies is needed to inform risk assessment methods.

Organochlorine Pesticides in Placentas from Southern Spain and Some Related Factors

During pregnancy, lipophilic xenobiotics stored in maternal adipose tissue can be mobilized and enter her blood circulation and reach the placenta. This study measured residues of oestrogen-mimicking organochlorine pesticides (OCs) in 150 placenta samples from women in Southern Spain. OCs were extracted from placenta by solid-liquid technique and purified by preparative liquid chromatography. Gas chromatography/electron-capture detection and mass spectrometry were used to identify and quantify p,p'-DDT and congeners/metabolites, endosulphan and congeners/metabolites, lindane, aldrin/dieldrin/endrin, hexachlorobenzene, methoxychlor and mirex. A mean of eight pesticides per placenta were detected (range, 3-15 pesticides). Endosulphan-ether, endosulphan-diol, endosulphan-I, p,p'-DDE, o,p'-DDD, p,p'-DDT, o,p'-DDT and lindane were detected in >or=50% of samples; p,p'-DDE was the most frequent (96.03%), followed by endosulphan-diol (76.86%) and lindane (74.17%). Presence of more pesticides was significantly associated with lower birth weight. Mean concentration of p,p'-DDE was 2.37+/-2.80 ng/g of placenta or 76.62+/-104.85 ng/g of lipid. Higher maternal body mass index was significantly associated with higher endosulphan concentrations in placenta, and greater maternal weight gain was significantly associated with higher p,p'-DDE concentrations. Prenatal exposure to OC xenoestrogens may be a causative factor in adverse reproductive health trends, and further studies are required to identify and describe pathways of this exposure to enhance preventive measures.

Organochlorine pesticides in serum and adipose tissue of pregnant women in Southern Spain giving birth by cesarean section

Since the appearance of DDT, increasingly potent insecticides have been developed to overcome the resistance developed by insects to successive products. Pesticides are also used in public health programs to control disease vectors. Despite legislation to control the use of certain products, they repeatedly appear in the adipose tissue, milk and serum of human populations. The present study determined the presence of organochlorine molecules in the adipose tissue, serum, and umblical cord of women giving birth by cesarean section in order to establish a possible correlation in organochlorine molecule content between these biological compartments and to examine fetal exposure to molecules with hormonal effects. Presence of nine organochlorines was detected by GC/ECD and confirmed by GC/MS. Highly significant differences (p<0.000) were observed between adipose tissue and maternal serum in concentrations of lindane, HCB, DDE, DDD, and endosulfan but not (p>0.5) in concentrations of endosulfan II or endosulfan sulfate. Only DDE concentrations differed (p<0.001) between maternal serum and umbilical cord serum. An association between pp'DDE and op'DDT was observed in maternal serum (p<0.094). An association in pp'DDE and pp'DDD content was found between adipose tissue and umbilical cord serum, and in pp'DDT content between adipose tissue and maternal serum. Results obtained indicate that exposure can be measured solely in serum when relatively high concentrations of pesticides are present.

Biological research on drug abuse and addiction in Hispanics: current status and future directions

Impressive progress has been made in the understanding of biological contributions to drug abuse and addiction. An area that has only recently begun to receive attention is potential ethnic and racial differences in biological systems that contribute to, or protect from, problem drug use. This article reviews recent research on drug abuse and addiction in Hispanics in which biological questions have been addressed, including work on genes, gene products (proteins), physiology and pharmacotherapy. Taken together, work to date suggests that there are both similarities and differences between Hispanics and other ethnic groups in biological factors related to drug abuse and addiction. Although the results are intriguing, relatively few studies have been done, and those that have been done have often been inconclusive due to low numbers of Hispanic subjects. Moreover, studies have often failed to recognize the complexity and heterogeneity of Hispanic populations in the United States and around the world. After reviewing the current status of the field, recommendations are given for future research in both humans and relevant animal models that will lead to a better understanding of drug abuse and addiction in Hispanics.

Phenoxyacetic acid herbicide exposure for women on Ontario farms

Women living and working on farms would be expected to have higher exposure to pesticides than the general nonoccupationally exposed population. Urinary concentrations of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and (4-chloro-2-methyl) phenoxyacetic acid (MCPA) were measured in 125 women living on farms in Ontario where these herbicides had recently been used for the first time that growing season. The women collected a spot urine void prior to the start of herbicide handling by spouses, followed by 2 consecutive 24-h urine samples. The pesticide applicator provided questionnaire data on pesticides that were used on the farm. Approximately 80% of the women had no detectable level of either herbicide in their urine. Geometric mean urinary concentrations of 2,4-D and MCPA in the d-2 samples were 0.7 microg/L. The responses to the questions on herbicide use on the farm were compared with urinary levels of the herbicide and the sensitivity for MCPA was determined to be 95-100%; however, the false positive rate for exposure was 70%. For 2,4-D, the sensitivity and specificity were approximately 70%, with a false positive rate of 30%. A simple question on whether the herbicide was used recently can accurately identify people who are likely not exposed; however, further research is required to be able to more validly predict those individuals who are exposed. Based on our study, it was concluded that exposure estimates based on questionnaire data alone may be fraught with uncertainties, which may differ depending on the particular pesticide of interest.

Detection of prenatal exposure to several classes of environmental toxicants and their metabolites by gas chromatography–mass spectrometry in maternal and umbilical cord blood

We developed a sensitive method to detect several classes of pesticides and their metabolites in maternal and cord whole blood using electron-impact gas chromatography-mass spectrometry (GC-MS). The method can detect parent and metabolite compounds at levels of <0.10 and 0.20mug/mL, respectively, with high accuracy and recovery. Analysis of blood from mother-infant dyads from an area of high pesticide use in the Philippines showed detectable levels of propoxur, 3-phenoxybenzoic acid (3-PBA), and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) in maternal and umbilical cord blood. GC-MS analysis of several classes of parent pesticides and their metabolites in maternal and cord blood provides a sensitive and specific method to detect pesticide exposure during pregnancy.

Exposure to pesticides and heavy work in greenhouses during pregnancy: does it effect birth weight?

OBJECTIVES

Work in greenhouses is performed in warm microclimate during the most time of the year, involves usually moderately intense or heavy work. The working conditions in greenhouses might involve also indirect exposure to pesticides resulting from contact with pesticide-treated flowers and vegetables. The aim of the study was to investigate whether the work in greenhouse during pregnancy adversely influenced infant birth weight and, if so, which of the two main potential hazards typical for such environment (heavy physical work or exposure to pesticides) played the major role in this process.

METHODS

The list of 14 major greenhouses (each above 5 ha) growing vegetables (cucumbers and tomatoes) was obtained from the Polish Chamber of Horticulture. Between January 2001 and December 2003, 460 women at the age below 45 years, married or who lived with a partner and who had been working for a period of at least 2 years in greenhouses in Poland were asked to participate in the project. We classified pregnancies of women working in, and out of, greenhouses on the basis of energy expenditure during mother's work into three groups: A (200-700 kcal/shift); B (701-1000 kcal/shift); and C (1001-1200 kcal/shift). Information about application of pesticides in 1997-2001 was received from persons responsible for chemical protection in each examined greenhouse. Trade names of pesticides, names and amounts of the active ingredients, type of cultivation and its area were abstracted from pesticide application registers run by each greenhouse operator. Pesticides were classified as reproductive and developmental (RD) toxins according to Pan American Pesticide Database classification.

RESULTS

The mean birth weight of infants whose mothers worked in greenhouse during pregnancy (work expenditure >1000 kcal/shift) was 177 g lower than that of those whose mothers worked out of greenhouse (light work <700 kcal/shift) (p = 0.05). Mothers who during work in greenhouse were potentially exposed to RD pesticides, delivered infants with birth weight lower by about 70 g. than infants' mothers not working at places where pesticides RD were applied, but these findings were not statistically significant.

CONCLUSION

Our results indicate that infants of mothers performing heavy work inside greenhouse during pregnancy had lower mean birth weight than infants of mothers working out of greenhouse. No similar effects of current exposure to pesticides was observed.

Analysis of endosulfan and its metabolites in rat plasma and selected tissue samples by gas chromatography-mass spectrometry

A method has been developed for the determination of trace levels of alpha-endosulfan, beta-endosulfan, endosulfan sulfate, and endosulfan diol in rat plasma and tissue samples. Endosulfan and its metabolites in the plasma samples were extracted with solid-phase extraction Chromabond-end-capped C18 cartridges and analyzed by a Shimadzu QP-5050A gas chromatograph-mass spectrometer (GCMS) with quadrupole detector in selected-ion-monitoring mode. The analysis of endosulfan and its metabolites in liver and kidney samples involved solvent extraction, Florisil solid-phase-extraction cleanup, and quantitation by GCMS. Recovery experiments for the plasma and tissue samples were conducted over concentration ranges of 10-100 ng mL(-1) and 100-1000 ng mL(-1), respectively. The method was applied to the analysis of trace levels of endosulfan and its metabolites in plasma and tissue samples collected from an animal study. Trace levels of alpha-endosulfan and beta-endosulfan in the ranges of undetectable to 3.11 microg g(-1) and undetectable to 1.19 microg g(-1), respectively, were detected in the kidney samples, whereas trace levels of endosulfan sulfate in the range of 0.02-0.22 microg g(-1) were detected in the liver samples of rats. Neither endosulfan nor its metabolites was detected in any of the plasma samples.

Ethical issues in conducting migrant farmworker studies

Migrant farmworkers should be considered a vulnerable population because they work in a hazardous industry, are often members of an ethnic minority, have known difficulty in accessing health care, and are often of lower socioeconomic status. For these reasons, too, it is extremely important to conduct health-related research with this often-underserved group. However, because migrant farmworkers are vulnerable, investigators must be especially vigilant in protecting them from the potential harms of research and in ensuring that the special ethical issues that arise in research with this population are identified and addressed for every project. In response to the National Cancer Institute's concerns about the feasibility of conducting epidemiologic studies among migrant farmworkers, researchers undertook four feasibility studies near the Texas-Mexico border. Each study raised different, complex ethical questions that challenged the investigators, but whose resolution turned out to be crucial to the success of the studies.

The use of pesticides in a Polish rural population and its effect on birth weight

INTRODUCTION

The risk of adverse reproductive outcomes related to pesticide exposure has been investigated in few studies; however, the results have not been consistent. The goal of the present study was to evaluate the influence of maternal residual exposure to pesticides on birth weight among women in an agricultural district in Central Poland.

METHOD

Subjects included 104 women who delivered a single, live infant between 1 January 1994 and 31 December 2000. Based on maternal reports, the type of farming (crops, orchards, non-farming jobs), involvement in field work and the trade names of pesticides used within last pregnancy were established. Birth weight for the most recent pregnancy was abstracted from the medical data of the local maternity unit.

RESULTS

Mothers who reported involvement in field work had a similar pregnancy duration but delivered infants with a significantly higher birth weight than mothers not reporting such activities in the first or second trimester of pregnancy (P=0.04). However, after controlling for pregnancy duration and other factors affecting birth weight, we found that maternal exposure to synthetic pyrethroids in the first or second trimester was associated with a small but statistically significant decrease in birth weight (P=0.02).

CONCLUSIONS

We postulate that the observed effect of pyrethroids exposure was related to a slower pace of foetal development corresponding to the small-for-gestational-age (SGA) birth.