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Human health risk assessments of exposures to non-carcinogenic occupational and environmental toxicants have mostly been undertaken using the Hazard Quotient (HQ) approach, which largely ignores variabilities in both exposures and associated adverse health outcomes, unlike probabilistic approaches. Chlorpyrifos is a neurotoxic insecticide that is commonly applied by farmers in Ghana with limited research on associated health risks among applicators. The objective of this study was to assess health risks associated with chlorpyrifos exposure among applicators on rice farms in Ghana, using advanced probabilistic approaches that incorporate variability in both exposure doses and adverse response doses obtained from human epidemiological studies. Urine samples obtained from the applicators were analyzed for 3,5,6-trichloro-2-pyridinol (TCP)from which Absorbed Daily Dose (ADD) and Lifetime Average Daily Dose (LADD) levels of chlorpyrifos were estimated. The scientific literature was searched to identify human epidemiological data from studies that have reported chlorpyrifos adverse effects and their corresponding exposure levels. Equivalent ADD and LADD of chlorpyrifos were estimated from the human epidemiological data to obtain chlorpyrifos Toxicant Sensitivity Distributions (TSDs). Using the applicators' chlorpyrifos dose distribution and TSDs, adverse health risks among the applicators were characterized using the probabilistic approaches, Overall Risk Probability (ORP) and Monte Carlo Simulation (MCS). The probabilities of chlorpyrifos adverse health effects occurring under the chronic exposure scenarios ranged from 1 to 8%, while those for acute exposure scenarios ranged from 31 to 34%. This study indicates that while the risks of chronic adverse health effects from chlorpyrifos exposure among the applicators were low, acute health risks were high., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Chlorpyrifos is one of the most widely used organophosphate pesticides and has a record of adverse effects on applicators. Assessment of exposure to chlorpyrifos based on its urinary metabolite, 3,5,6-trichloro-2-pyridinol (TCP), is considered as the most accurate. However, urine sampling can be difficult, and the laboratory analytical procedures involved are complex and expensive. A simpler approach for assessing pesticide exposure among applicators is the whole-body dermal dosimetry method, but this needs validation. The objective of this study was to compare chlorpyrifos exposure estimates obtained separately with the urinary TCP and the whole-body dermal dosimetry methods from applicators. Exposure estimates from the whole-body dermal dosimetry method (5-29 μg/kg/day) showed less variation than those from the urinary TCP method (1-71 μg/kg/day), but both were in close agreement at the mean level (16 μg/kg/day and 15 μg/kg/day, respectively). The whole-body dermal dosimetry method is therefore valid for providing estimates of the typical levels of pesticide exposure among applicators in situations where the urinary TCP method cannot be applied., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Chlorpyrifos is a neurotoxic insecticide that is widely used in the agricultural sector of Ghana. The main objective of this study was to evaluate the levels of chlorpyrifos exposure and health risk among applicators (n = 21) on irrigated rice farms in Ghana, based on a typical application event. Pre- and post-application urine samples (24-h) were collected from the applicators and analysed for 3,5,6-trichloro-2-pyridinol (TCP), using LC-MS/MS. The levels of chlorpyrifos-absorbed dose with the applicators were estimated from the urinary TCP levels. Prior to application, the median absorbed dose of chlorpyrifos (background exposure) with the applicators was 0.2 μg/kg/day (range 0.05 to 2 μg/kg/day). Following application, the median absorbed dose of chlorpyrifos (application exposure) increased 30-fold to 6 μg/kg/day (range 0.7 to 74 μg/kg/day). The mean elimination half-life (t 1/2 ) of chlorpyrifos was calculated to be 50 h. Hazard quotient (HQ) values (HQ > 1) obtained with the chronic (10 μg/kg/day) and acute (100 μg/kg/day) guideline values of the WHO suggested no risk of chronic or acute health effects, respectively, among both the median and 5% highly exposed groups. However, HQ values (HQ > 1) obtained with the chronic (0.3 μg/kg/day) and acute (5 μg/kg/day) guideline values of the USEPA suggested risk of chronic and acute health effects, respectively, among both the median and 5% highly exposed groups. The quantity of chlorpyrifos formulation applied, spraying duration, and the number of spray tanks applied significantly correlated with the absorbed dose levels of chlorpyrifos from application exposure. Therefore, these factors suggest means to reduce exposure and consequent health risk among the applicators.

Generally, there is limited information on pesticide absorbed dose levels and health risk attributable to the dermal route of exposure among applicators. The objective of this study was to evaluate the absorbed dose levels and consequent health risk from dermal exposure to chlorpyrifos among applicators on rice farms in Ghana. The whole-body dosimetry technique was used to capture chlorpyrifos residues penetrating the applicators' clothing and reaching their skin, as well as residues reaching uncovered body areas of the applicators. Acute (ADD D ) and chronic (LADD D ) absorbed dose levels of chlorpyrifos were estimated from the residues and plotted as cumulative probability distributions. Health risk from chlorpyrifos exposure was characterized using the Hazard Quotient (HQ) technique. Three of the four acute exposure guideline values used in the study indicated that applicators, represented by the median-exposed (ADD D , 15 μg/kg/day) and the 5% - highly exposed (ADD D , 27 μg/kg/day) groups were at high risk of acute adverse health effects due to chlorpyrifos exposure, with HQ values ranging from 1.5 to 5 and 2.7 to 9, respectively. Regarding chronic adverse health effects, none of the guideline values suggested risk among the median-exposed group (LADD D , 0.3 μg/kg/day), with HQ values ranging from 0.03 to 1. However, two of the chronic exposure guideline values suggested that the 5%- highly exposed group (LADD D , 0.6 μg/kg/day) may be adversely affected, with HQ values ranging from 1.2 to 2. These findings highlight the importance of the dermal route as a major pesticide exposure pathway and suggest possible exposure minimization strategies., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Studies evaluating dermal exposure to pesticides among applicators in tropical countries have largely been conducted using the patch dosimetry and hand wiping/washing techniques. This study used the more accurate whole-body dosimetry technique to evaluate dermal exposure to chlorpyrifos among applicators on rice farms in Ghana. The exposure levels were plotted as Cumulative Probability Distribution (CPD). Total Dermal Exposure (TDE) of chlorpyrifos among the median exposed and the 5% highly exposed groups during a spray event were 24 mg and 48 mg, respectively. When these were converted as a percentage of the quantity of active ingredient applied (Unit Exposure, UE), UE values of 0.03% and 0.06% were found among the median exposed and the 5% highly exposed groups, respectively. Overall, the hands were the most contaminated anatomical regions of the applicators, both in terms of proportion of TDE (39%) and skin loading (13 μg/cm 2 ). Also, the lower anatomical region was more contaminated (82% of TDE) compared to the upper anatomical region (18% of TDE). The levels of chlorpyrifos TDE among the applicators were found to be influenced by the quantity of insecticide applied and the height of the crops sprayed (p < 0.05). The pesticide UE data of the present study can be used to estimate the levels of dermal exposure under similar pesticide use scenarios among applicators. The findings of the present study suggest that protecting the hands and the lower anatomical regions with appropriate PPE may significantly reduce exposure among applicators., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Chlorpyrifos has been used extensively for decades to control crop pests and disease-transmitting insects; its contribution to increasing food security and minimizing the spread of diseases has been well documented. Pymetrozine and Avermectin (also known as abamectin) have been used to replace the toxic organophosphate insecticides (e.g., Chlorpyrifos) applied to rice crops in China, where the overuse of pesticides has occurred. In addition, climate change has exacerbated pesticide use and pollution. Thus, farmers and communities are at risk of exposure to pesticide pollution. This study reviews the contamination, exposure, and health risks through environmental and biological monitoring of the legacy pesticide Chlorpyrifos and currently used insecticides Pymetrozine and Avermectin in China; it investigates whether changes in pesticide usage from Chlorpyrifos to Pymetrozine and Avermectin reduce pesticide contamination and health hazards to communities and residents. In addition, this review discusses whether Pymetrozine and Avermectin applications could be recommended in other countries where farmers largely use Chlorpyrifos and are exposed to high health risks under climate change scenarios. Although Chlorpyrifos is now banned in China, farmers and residents exposed to Chlorpyrifos are still experiencing adverse health effects. Local farmers still consider Chlorpyrifos an effective pesticide and continue to use it illegally in some areas. As a result, the concentration levels of Chlorpyrifos still exceed risk-based thresholds, and the occurrence of Chlorpyrifos with high toxicity in multiple environmental routes causes serious health effects owing to its long-term and wide application. The bioaccumulation of the currently used insecticides Pymetrozine and Avermectin in the environment is unlikely. Pymetrozine and Avermectin used in paddy water and soil for crop growth do not pose a significant hazard to public health. A change in pesticide use from Chlorpyrifos to Pymetrozine and Avermectin can reduce the pesticide contamination of the environment and health hazards to communities and residents. Finally, we recommend Pymetrozine and Avermectin in other countries, such as Vietnam, and countries in Africa, such as Ghana, where farmers still largely use Chlorpyrifos. [ABSTRACT FROM AUTHOR]