Maria Luisa Feo

Pyrethroids in human breast milk: Occurrence and nursing daily intake estimation.

There is an assumption that pyrethroid pesticides are converted to non-toxic metabolites by hydrolysis in mammals. However, some recent works have shown their bioaccumulation in human breast milk collected in areas where pyrethroids have been widely used for agriculture or malaria control. In this work, thirteen pyrethroids have been studied in human breast milk samples coming from areas without pyrethroid use for malaria control, such as Brazil, Colombia and Spain. The concentrations of pyrethroids ranged from 1.45 to 24.2 ng g⁻¹ lw. Cypermethrin, λ-cyhalothrin, permethrin and esfenvalerate/fenvalerate were present in all the studied samples. The composition of pyrethroid mixture depended on the country of origin of the samples, bifenthrin being the most abundant in Brazilian samples, λ-cyhalothrin in Colombian and permethrin in Spanish ones. When the pyrethroid concentrations were confronted against the number of gestations, an exponential decay was observed. Moreover, a time trend study was carried out in Brazil, where additional archived pool samples were analyzed, corresponding to years when pyrethroids were applied for dengue epidemic control. In these cases, total pyrethroid levels reached up to 128 ng g⁻¹ lw, and concentrations decreased when massive use was not allowed. Finally, daily intake estimation of nursing infants was calculated in each country and compared to acceptable WHO levels. The estimated daily intakes for nursing infants were always below the acceptable daily intake levels, nevertheless in certain samples the detected concentrations were very close to the maximum acceptable levels.

Dechlorane Plus and related compounds in aquatic and terrestrial biota: a review.

Dechlorane Plus, dechlorane 602, dechlorane 603 and dechlorane 604 are flame retardants that have been used for a long time as a substitute for mirex, but they have not been noticed as environmental contaminants until recently (2006). Regardless of their large molecular size and very high lipophilicity (log KOW > 9), Dechlorane Plus and related compounds have been detected in different aquatic and terrestrial species, supporting their bioaccumulation and biomagnification. Moreover, some studies showed different behaviour of the syn-Dechlorane Plus and anti-Dechlorane Plus isomers in the environment and different biomagnification factors in biota. This review describes the different analytical approaches applied to the determination of Dechlorane Plus and related compounds. Moreover, a summary of their levels in aquatic and terrestrial biota, as well as in humans, is presented, showing also current research results on their bioaccumulation and biomagnification potential. Finally, isomer-specific bioaccumulation of Dechlorane Plus is also discussed.

Pyrethroids: a new threat to marine mammals?

The present study constitutes the first investigation to demonstrate pyrethroid bioaccumulation in marine mammals, despite the assumption that these insecticides are converted to non-toxic metabolites by hydrolysis in mammals. Twelve pyrethroids were determined in liver samples from 23 male franciscana dolphins from Brazil. The median concentration values for total pyrethroids were 7.04 and 68.4 ng/g lw in adults and calves, respectively. Permethrin was the predominant compound, contributing for 55% of the total pyrethroids. Results showed a distinct metabolic balance of pyrethroids through dolphin life. High loads are received at the beginning of their lives and, when they reach sexual maturity, these mammals seem to degrade/metabolize pyrethroids. Maternal transfer of these compounds was also evaluated through the analysis of breast milk and placenta samples. Pyrethroids were detected in both matrices, with values between 2.53-4.77 ng/g lw and 331-1812 ng/g lw, respectively. Therefore, for the first time, a study shows mother-to-calf transfer of pyrethroids by both gestational and lactation pathways in dolphins.

Biotransformation of BDE-47 to Potentially Toxic Metabolites Is Predominantly Mediated by Human CYP2B6

Background: Previous studies have indicated that cytochrome P450s (CYPs) are involved in the metabolism of polybrominated diphenyl ether (PBDE) flame retardants in humans, resulting in the formation of hydroxylated PBDEs (OH-PBDEs) that are potentially more toxic than the parent PBDEs. However, the specific enzymes responsible for the formation of OH-PBDEs are unknown. Objectives: The purposes of this study were to characterize the in vitro metabolism of 2,2´,4,4´-tetrabromodiphenyl ether (BDE-47) by human liver microsomes (HLM) and recombinant human CYPs, and to identify the CYP(s) that are active in the oxidative metabolism of BDE-47. Methods: Recombinant human CYPs (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4) were incubated with BDE-47 (20 µM), and the metabolites were measured and characterized using gas chromatography with tandem mass spectrometry (GC-MS/MS). For kinetic studies, CYP2B6 and pooled human liver microsomes (HLMs) were incubated with BDE-47 (0–60 µM). Results: CYP2B6 was the predominant CYP capable of forming six OH-BDEs, including 3-OH-BDE-47, 5-OH-BDE-47, 6-OH-BDE-47, 4-OH-BDE-42, 4´-OH-BDE-49, and a metabolite tentatively identified as 2´-OH-BDE-66. On the basis of full-scan GC-MS analysis, we hypothesized the formation of two other metabolites: di-OH-tetra-BDE and di-OH-tetrabrominated dioxin. In kinetic studies of BDE-47 metabolism by CYP2B6 and pooled HLMs, we found Km values ranging from 3.8 to 6.4 µM and 7.0 to 11.4 µM, respectively, indicating the high affinity toward the formation of OH-BDEs. Conclusion: Our findings support a predominant role of CYP2B6 in the metabolism of BDE-47 to potentially toxic metabolites, including a hypothesized di-OH-tetrabrominated dioxin metabolite. These results will assist future epidemiological studies investigating the potential of PBDEs and their metabolites to produce neurobehavioral/neurodevelopmental disorders.

A rapid and sensitive analytical method for the determination of 14 pyrethroids in water samples

A simple, efficient and environmentally friendly analytical methodology is proposed for extracting and preconcentrating pyrethroids from water samples prior to gas chromatography-negative ion chemical ionization mass spectrometry (GC-NCI-MS) analysis. Fourteen pyrethroids were selected for this work: bifenthrin, cyfluthrin, lambda-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fenvalerate, fenpropathrin, tau-fluvalinate, permethrin, phenothrin, resmethrin, tetramethrin and tralomethrin. The method is based on ultrasound-assisted emulsification-extraction (UAEE) of a water-immiscible solvent in an aqueous medium. Chloroform was used as extraction solvent in the UAEE technique. Target analytes were quantitatively extracted achieving an enrichment factor of 200 when 20 mL aliquot of pure water spiked with pyrethroid standards was extracted. The method was also evaluated with tap water and river water samples. Method detection limits (MDLs) ranged from 0.03 to 35.8 ng L(-1) with RSDs values < or =3-25% (n=5). The coefficients of estimation of the calibration curves obtained following the proposed methodology were > or =0.998. Recovery values were in the range of 45-106%, showing satisfactory robustness of the method for analyzing pyrethroids in water samples. The proposed methodology was applied for the analysis of river water samples. Cypermethrin was detected at concentration levels ranging from 4.94 to 30.5 ng L(-1).

Pyrethroid use-malaria control and individual applications by households for other pests and home garden use

Presence of pyrethroid insecticides in human breast milk and in thatch wall material of dwellings from Southern Africa subtropical area (Manhiça, Mozambique) was investigated to assess potential pyrethroid route of human exposure. Human breast milk samples were collected during 2002 when pyrethroids were widely used as insecticides for mosquito bed nets in Mozambique for malaria control. The median concentration value of total pyrethroids ranged between 87 and 1200ng/glw, with λ-cyhalothrin being the most predominant pyrethroid in human breast milk contributing for 35% of the total amount. Moreover, and for the first time, an isomer-specific enrichment was found in human breast milk, showing a selective isomeric accumulation or metabolism in the human body. Based on the calculated pyrethroid concentrations in human breast milk, the daily ingestion rate of pyrethroid was estimated. The nursing infant dietary intake ranged from 0.67 to 9.0μg(kg of body weight)(-1)day(-1). In addition, thatch materials collected after the reintegration of dichlorodiphenyltrichloroethene (DDT) as insecticide residual spraying (IRS) in Mozambique, showed the presence of pyrethroids with concentration values ranging between 6.9 and 700ng/gdw. In thatch material as well as in human breast milk, pyrethroid contamination was mainly attributed to the agriculture usage of this insecticide knowing that agriculture represent the 80% of the economy in Mozambique. However, a possible usage of this insecticide as IRS in Mozambique cannot be excluded despite their low efficiency for malaria control. The continued use of these compounds (both for agriculture and malaria prevention) and the ingestion rates calculated from the breast milk concentrations indicate that these insecticides cannot be overlooked for the assessment of the lactation risks of breastfeeding infants from the Manhiça region.

Development of a liquid chromatography-electrospray chemical ionization tandem mass spectrometry analytical method for analysis of eleven hydroxylated polybrominated diphenyl ethers.

Recently, hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have emerged as environmentally relevant pollutants due to recent reports of their natural production and metabolism. Recent mechanistic studies in human and rats have shown that some OH-PBDEs are more potent than parent compounds (PBDEs) and may contribute substantially to neurodevelopmental disorders by direct neurotoxicity, or indirectly through altered thyroid disruption. However, analytical methodologies for determination of OH-PBDEs are currently limited. In this study a robust liquid chromatography-electrospray tandem triple quadrupole-linear ion trap mass spectrometer (LC-ESI-QqLIT-MS-MS) in negative mode method was developed for the determination of eleven OH-tri- to OH-hexa-PBDEs. Two different columns were tested and compared for chromatographic separation: a C18 BetaBasic and a Purospher STAR RP 18, working at pH 8 and 10, respectively. Mobile phase (acetonitrile:water) was optimized by changing the pH of the aqueous phase and the concentration of the organic modifier (methanol). The MS-MS parameters (declustering potential (DP), collision energy (CE) and cell exit potential (CXP)) were optimized. Selected reaction monitoring (SRM) was used in order to increase sensitivity. Two SRM transitions ([M-H](-)>[Br](-)) were selected for each OH-PBDE, one for quantification and the second one for confirmation. Under the optimized conditions, the instrumental limits of detection were between 0.17 and 0.72injectedpg. The method provided good linearity (r>0.99 for a concentration range of 0.30-100ng/mL), accuracy and precision (%Dev and %RSD≤20% for intra- and inter-assays).

Organic carbon content effects on bioavailability of pyrethroid insecticides and validation of Solid Phase Extraction with Poly (2,6-diphenyl-p-phenylene oxide) Polymer by Daphnia magna toxicity tests

Solid phase extraction with Poly (2,6-diphenyl-p-phenylene oxide) Polymer (Tenax) was used for determining the bioavailability of eleven pyrethroids in field collected sediments with different organic carbon content (OC). The bioavailable fraction of pyrethroids decreased with increasing OC in sediments; the percentages of desorption ranged from 10 to 20% for sediment with higher OC content (5.8%) and 15-40% for that with lower OC (2%). Generally pyrethroids showed low bioavailability and cyfluthrin resulted to be the most bioavailable among the studied pyrethroids. Acute toxicity tests with Daphnia magna were carried out on sediment spiked with three selected pyrethroids (λ-cyhalothrin, cypermethrin and deltamethrin) and served to validate the efficiency of Tenax as a method for assessing the bioavailability of pyrethroids. Toxicity test demonstrated that Tenax was able to remove the toxic bio-available fraction of pyrethroids in sediment. Extracts from Tenax beads after the desorption experiments and spiked sediment before desorption had an equivalent toxicity (LC50) to D. magna neonates at 48 and 72 h of exposure. These results indicate that Tenax beds can be used to predict bio-available and toxic fractions of pyrethroids sorbed to sediments to aquatic organisms like D. magna.

Population Growth Rate Responses of Ceriodaphnia dubia to Ternary Mixtures of Specific Acting Chemicals: Pharmacological versus Ecotoxicological Modes of Action

When considering joint toxic apical effects at higher levels of biological organization, such as the growth of populations, the so-called pharmacological mode of action that relies on toxicological mechanistic effects on molecular target sites may not be relevant. Such effects on population growth rate will depend on the extent to which juvenile and adult survival rates and production rates (juvenile developmental rates and reproduction) are affected by toxic exposure and also by the sensitivity of population growth rates to life-history changes. In such cases, the ecotoxicological mode of action, defined as the crucial life-history trait processes and/or xenobiotic-life-history trait interactions underlying a toxicological effect on population growth rate, should be considered. Life-table response experiments with the crustacean Ceriodaphnia dubia exposed to single and ternary mixtures of nine compounds were conducted to test the hypothesis that joint effects on population growth rates could be predicted from the mixture constituent ecotoxicological mode of action. Joint effects of mixtures containing pharmacologically dissimilar compounds (cadmium, λ-cyhalothrin, and chlorpyrifos) that differentially affected life-history traits contributing to population growth rates were accurately predicted by the independent-action concept. Conversely, the concentration-addition concept accurately predicted joint effects of two different mixtures: one containing pharmacologically similar acting pyrethroids that also affected similarly life-history traits, the other one that included pharmacologically dissimilar compounds (3,4-dichloroaniline, sodium bromide, and fenoxycarb) acting mainly on reproduction rates. These results indicate that when assessing combined effects on population growth rate responses, selection of mixture toxicity conceptual models based on the ecotoxicological mode of action of mixture constituents provided more accurate predictions than those based on the pharmacological mode of action.