Screening of pesticide distributions in foods of animal origin: a matrix-based approach for biotransfer factor modeling of grazing mammals

Introducing internal allocation factors for assessing aggregate pesticide exposure across multiple pathways and routes

In the health risk assessment of pesticides, methods for external exposure assessment have been well developed. However, quantifying the contribution of various exposure pathways or routes to internal dose remains challenging. This study introduced the internal allocation factor (IAF) for 319 pesticides to investigate the impact of different exposure pathways and routes on chemical distribution within the human body. The IAFs can be calculated from various exposure sources (or pathways), routes, and biological samples. Analysis of different exposure sources revealed that crop exposure generally had the lowest IAF in organs and tissues, indicating a high contribution to the internal dose. The median IAF values for crop exposure in blood, liver, lung, kidney, fat, and muscle were all around 1.05. For three exposure routes of soil pesticide, the results found that IAF values for oral and dermal exposure routes were significantly lower than those for inhalation exposure. When the pesticide concentrations in biological samples are known, IAF can be utilized to back-calculate the pesticide levels in other organs and tissues. The results show that under a single exposure route, the concentration factor varies greatly between organs or tissues due to differences in compositions of human tissues (e.g., water and lipid contents) and pesticide properties (e.g., hydrophilicity and lipophilicity).

A systematic review of pesticide exposure, associated risks, and long-term human health impacts

Pesticides are widely used to control pests, but their widespread use raises concerns regarding potential health risks for humans. There are several routes through which pesticides can be ingested, inhaled, and absorbed, resulting in acute and long-term health consequences. This systematic review synthesizes the available evidence regarding the health risks and long-term effects of pesticide exposure, with a particular focus on epidemiological and toxicological studies. A systematic review was conducted by searching scientific databases i.e. Scopus, and Web of Science for peer-reviewed articles published between 2000 and 2024. Studies were selected based on their focus on pesticide exposure, health risks, and long-term effects. Meta-analysis was conducted where sufficient homogeneity of outcomes allowed. This review identified consistent associations between chronic pesticide exposure and non-communicable diseases, including cancer, neurological disorders, and endocrine disruptions. An increased incidence of respiratory issues and neurodegenerative diseases was often associated with occupational exposure to pesticides. People exposed for a prolonged or high intensity time period, particularly agricultural workers, were more likely to experience long-term health effects. There are a number of factors that influences the ability to draw definitive conclusions, including variations in pesticide types, exposure levels, and health outcomes. Chronic exposure to pesticides presents significant health risks, particularly for individuals in high-exposure environments like agriculture. While evidence indicates strong associations with several long-term health conditions, additional research is necessary to elucidate dose-response relationships and mechanisms of action. This review underscores the necessity for enhanced regulatory measures and improved safety protocols to mitigate pesticide-related health risks.

Assessing chronic gestational exposure to environmental chemicals in pregnant women: Advancing the co-PBK model

Vulnerable populations, such as pregnant women and their fetuses, confront potential health risks due to exposure to environmental toxic compounds. Computational methods have been popular in assessing chemical exposure to populations, contrasting with traditional cohort studies for human biomonitoring. This study proposes a screening-level approach based on physiologically based kinetic (PBK) modeling to evaluate the steady-state exposure of pregnant women to environmental chemicals throughout pregnancy. To exemplify the modeling application, naphthalene was chosen. Simulation results indicated that maternal fat exhibited significant bioaccumulation potential, with the log-transformed BTF of naphthalene at 0.51 mg kg-1 per mg d-1 in the steady state. The placenta was primarily exposed to 0.83 mg/d naphthalene for a 75.2 kg pregnant woman, considering all exposure routes. In the fetal structure, single-organ fetal PBK modeling estimated a naphthalene exposure of 123.64 mg/d to the entire fetus, while multiple-organ fetal PBK modeling further revealed the bioaccumulation highest in fat tissue. The liver identified as the vital organ for metabolism, kBioT,LiverM was demonstrated with the highest sensitivity among rate constants in the maternal body. Furthermore, the first-order kinetic rate constants related to the placenta and blood were found to impact the distribution process of naphthalene in the fetus, influencing gestational exposure. In conclusion, urgent attention is needed to develop a computational biomonitoring tool for assessing toxic chemical exposure in vulnerable populations.

Mechanistic modelling of amphibian body burdens after dermal uptake of pesticides from soil

Amphibians are currently considered to be covered by pesticide Environmental Risk Assessment schemes by surrogacy assumptions of exposure and susceptibility based on typical laboratory test species such as fish, mammals, and birds. While multiple reviews have shown for this approach to be adequate in the case of aquatic stages, the same cannot be definitively stated for terrestrial stages. Concerns have risen that exposure of amphibians is likely to be highly influenced by dermal absorption, primarily due to the high permeability of their skin and the lack of a protective layer, such as fur or feathers. It is thus hypothesized that dermal uptake could be a significant route of exposure. Consequently, it is necessary to determine the relative importance of different exposure routes that might affect the integrated toxicity outcome for terrestrial amphibian life-stages. Here, a one-compartment Toxicokinetic model was derived and tested using a publicly available dataset containing relevant exposure and uptake information for juvenile anurans exposed to 13 different pesticides. Modelled body burdens were then compared to measured burdens for a total of 815 individuals. Overall, a good concordance between modelled and measured values was observed, with the predicted and measured body burdens differing by a factor of 2 on average (overall R2 of 0.80 and correlation coefficient of 0.89), suggesting good predictivity of the model. Accordingly, the model predicts realistic body burdens for a variety of frog and toad species, and overall, for anurans. As the model includes rehydration (implicit in the evaluated studies) but currently does not account for metabolism, it can be seen as a worst-case assessment. We suggest toxicokinetic models, such as the one here presented, could be used to characterize dermal exposure in amphibians, screen for pesticides of concern, and prioritize risk assessment efforts, whilst reducing the need for de novo vertebrate testing.

Co-PBK: a computational biomonitoring tool for assessing chronic internal exposure to chemicals and metabolites

Toxic chemicals are released into the environment through diverse human activities. An increasing number of chronic diseases are associated with ambient pollution, thus posing a threat to people. Given the high consumption of resources for human biomonitoring, this study proposed coupled physiologically-based kinetic (co-PBK) modeling matrices as a biomonitoring tool for simplifying chronic internal exposure estimates of environmental chemicals and their metabolites using naphthalene (NAP) and its metabolites (i.e., 1-OHN and 2-OHN) as simulation examples. According to the simulation of the steady-state mass among various organs/tissues via the co-PBK modeling matrices, fat had the highest potential bioaccumulation of NAP and its metabolites. With respect to body fluids, 1-OHN and 2-OHN tended to bioaccumulate more in the bile than in the urine. According to the sensitivity analysis, the calculated sensitivity factors for the first-order kinetics-based rate constants imply that due to the biotransformation process, target organs/tissues (e.g., liver and kidneys) would be continuously exposed to more NAP metabolites under chronic exposure. Meanwhile, 1-OHN may be more stably transported to the urine than 2-OHN for further human biomonitoring during long-term internal exposure. According to the case study of simulating population chronic exposure to NAP in Shenzhen, the co-PBK modeling estimated the population exposure to NAP with an intake rate of 8.77 × 10-2 mg d-1 and the aggregated urinary concentration of NAP metabolites of 2.60 μg L-1. Furthermore, the accuracy of the urinary levels between the real-world data and the values simulated by the co-PBK modeling was assessed and the root-mean-square error of c1-OHN,urine was found to be lower than that of c2-OHN,urine.

Occurrence of resorcyclic acid lactones in porcine urine: discrimination between illegal use and contamination

Zeranol (α-zearalanol, α-ZAL), is a resorcyclic acid lactone (RAL). Its administration to farm animals to improve meat production has been prohibited in the European Union due to the potential risk to human health. However, it has been demonstrated that α-ZAL may be present in livestock animals due to Fusarium fungi that produce fusarium acid lactones contamination in feed. The fungi produce a small amount of zearalenone (ZEN), which is metabolized to zeranol. The potential endogenous origin of α-ZAL makes it difficult to correlate positive samples to a potential illicit treatment with α-ZAL. We present two experimental studies that investigated the origin of natural and synthetic RALs in porcine urine. Urine samples from pigs that were either fed with ZEN-contaminated feed or administered α-ZAL by injection were analyzed by liquid chromatography coupled to tandem mass spectrometry, with the method validated according to Commission Implementing Regulation (EU) 2021/808. The data show that although the concentration of α-ZAL in the ZEN feed-contaminated samples is significantly lower than in the illicit administration samples, α-ZAL can occur in porcine urine via natural metabolism. Additionally, the feasibility of using the ratio of forbidden/fusarium RALs in porcine urine as a reliable biomarker for illicit treatment with α-ZAL administration was evaluated for the first time. This study demonstrated that the obtained ratio in the contaminated ZEN feed study was close to 1, while in the illegally administered α-ZAL samples the ratio is always higher than 1 (up to 135). Therefore, this study proves that the ratio criteria (already used when a forbidden RAL is detected in bovine urine) may also be used for porcine urine.

Considering degradation kinetics of pesticides in plant uptake models: proof of concept for potato

BACKGROUND

Degradation kinetics of pesticides in plants are crucial for modeling mechanism-based pesticide residual concentrations. However, due to complex open-field conditions that involve multiple pesticide plant uptake and elimination processes, it is difficult to directly measure degradation kinetics of pesticides in plants. To address this limitation, we proposed a modeling approach for estimating degradation rate constants of pesticides in plants, using potato as a model crop. An operational tool was developed to backward-estimate degradation rate constants, and three pesticides were selected to perform example simulations.

RESULTS

The simulation results of thiamethoxam indicated that the growth dynamics of the potato had a significant impact on the degradation kinetic estimates when the pesticide was applied during the early growth stage, as the size of the potato determined the uptake and elimination kinetics via diffusion. Using mepiquat, we demonstrated that geographical variations in weather conditions and soil properties led to significant differences in the dissipation kinetics in both potato plants and soil, which propagated the variability of the degradation rate constant. Simulation results of chlorpyrifos differed between two reported field studies, which is due to the effect of the vertical distribution of the residue concentration in the soil, which is not considered in the majority of recent studies.

CONCLUSIONS

Our proposed approach is adaptable to plant growth dynamics, preharvest intervals, and multiple pesticide application events. In future research, it is expected that the proposed method will enable region-specific inputs to improve the estimation of the degradation kinetics of pesticides in plants. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Biopesticides as a promising alternative to synthetic pesticides: A case for microbial pesticides, phytopesticides, and nanobiopesticides

Over the years, synthetic pesticides like herbicides, algicides, miticides, bactericides, fumigants, termiticides, repellents, insecticides, molluscicides, nematicides, and pheromones have been used to improve crop yield. When pesticides are used, the over-application and excess discharge into water bodies during rainfall often lead to death of fish and other aquatic life. Even when the fishes still live, their consumption by humans may lead to the biomagnification of chemicals in the body system and can cause deadly diseases, such as cancer, kidney diseases, diabetes, liver dysfunction, eczema, neurological destruction, cardiovascular diseases, and so on. Equally, synthetic pesticides harm the soil texture, soil microbes, animals, and plants. The dangers associated with the use of synthetic pesticides have necessitated the need for alternative use of organic pesticides (biopesticides), which are cheaper, environment friendly, and sustainable. Biopesticides can be sourced from microbes (e.g., metabolites), plants (e.g., from their exudates, essential oil, and extracts from bark, root, and leaves), and nanoparticles of biological origin (e.g., silver and gold nanoparticles). Unlike synthetic pesticides, microbial pesticides are specific in action, can be easily sourced without the need for expensive chemicals, and are environmentally sustainable without residual effects. Phytopesticides have myriad of phytochemical compounds that make them exhibit various mechanisms of action, likewise, they are not associated with the release of greenhouse gases and are of lesser risks to human health compared to the available synthetic pesticides. Nanobiopesticides have higher pesticidal activity, targeted or controlled release with top-notch biocompatibility and biodegradability. In this review, we examined the different types of pesticides, the merits, and demerits of synthetic pesticides and biopesticides, but more importantly, we x-rayed appropriate and sustainable approaches to improve the acceptability and commercial usage of microbial pesticides, phytopesticides, and nanobiopesticides for plant nutrition, crop protection/yield, animal/human health promotion, and their possible incorporation into the integrated pest management system.

Framework for defining pesticide maximum residue levels in feed: applications to cattle and sheep

BACKGROUND

Pesticide residues in animal feed can endanger animal health and compromise the safety of livestock products for human consumption. Even though policymakers such as the European Union and the World Health Organization have established maximum residue levels (MRLs) for pesticides in both human food and animal feed, there is no systematic management of pesticides in animal feed that considers the entire supply chain. In response, we propose a framework for defining consistent MRLs for pesticides in animal feed that assesses the impact of defined MRLs on upstream (e.g., MRLs in feed crops) and downstream (e.g., MRLs in livestock products) sectors of the livestock-product supply chain.

RESULTS

The MRLs determined for the selected pesticides in the feed of cattle and sheep as case study animals indicate that lipophilic pesticides tend to have lower MRLs than hydrophilic pesticides, primarily due to the relatively high toxicity and biotransfer factors of lipophilic pesticides. In addition, we observe that, primarily for lipophilic pesticides, upstream and downstream regulations are not aligned in terms of defining MRLs in feed using current MRLs in crops with relevance to feed and foods of animal origin.

CONCLUSION

Some of the current pesticide regulations in the livestock-product supply chain need to be re-evaluated to ensure that MRLs in the upstream sector (i.e., crops) do not result in unacceptable residues in the downstream sector (i.e., MRLs in livestock products affecting animal and human health). Finally, we provide recommendations for optimizing the derivation of MRLs in feed, including the evaluation of residue fate during feed and food manufacturing processes. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluating sulfoxaflor residues in pig tissues using animal modeling

Maximum residue limits (MRL) for pesticides in feed have been set to protect public health and produce safe livestock products. In vivo experiments to establish MRL are essential, as livestock are commonly used to obtain reliable In vivo quantitative information. Here, we aimed to evaluate whether small laboratory animals can replace or reduce monogastric livestock in experiments to quantify pesticide residues In vivo after oral consumption through feed. First, 24 pigs and rats were randomly assigned to four groups and fed 0, 3, 9, or 30 mg/kg of sulfoxaflor. After four weeks, serum, muscle, fat, liver, kidney, and small intestine samples were collected, and sulfoxaflor residues were analyzed using liquid chromatography - tandem mass spectrometry. Sulfoxaflor residues in pig tissues were significantly correlated with those in rat tissues. Model equations were formulated based on the residual sulfoxaflor amount in pig and rat tissues. The calculated and measured sulfoxaflor residues in pigs and rats showed more than 90% similarity. Sulfoxaflor did not affect body weight gain, feed intake, or the feed conversion ratio. Therefore, we concluded that pesticide residue quantification in vivo to establish MRL could be performed using small laboratory animals instead of livestock animals. This would contribute to obtaining In vivo pesticide residue information and reducing large-scale livestock animal experiments.