Biomonitoring of chlorpyrifos exposure and health risk assessment among applicators on rice farms in Ghana

Abstract

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) 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.

Assessment of occupational exposure to pesticides applied in rice fields in developing countries: a critical review

“…Under field conditions, total amount or concentration of pesticides applied has been consistently identified as the primary influence on occupational exposure among applicators (Colosio et al 2012;Phung et al 2012a;Atabila et al 2019). There are also positive and significant associations between adsorbed daily doses during application and both the duration of spraying and the number of spray tanks filled (Spearman correlation coefficient (r): 0.53 -0.59; p-value < 0.05; Atabila et al 2018b). Application parameters including duration of pesticide spraying (0.5 -1 hour per day), type of sprayer (backpack sprayer > hand sprayer), type of pesticide, and time of spraying period (early morning) were significantly associated with the levels of blood cholinesterase in a group of 33 rice farmers studied in Thailand (p-value < 0.033; Sombatsawat et al 2014).…”

“…Based on measured urinary TCP concentrations, the predicted baseline and post-application exposures to chlorpyrifos were 3.0 x 10 -5 -2.0 x 10 -3 mg kg -1 day -1 and 3.5 x 10 -4 -9.4 x 10 -2 mg kg -1 day -1 , respectively. The estimated baseline exposure can be used to correct the occupational exposure for the background exposure (Atabila et al 2018b), thus allowing risk assessment due to a typical pesticide handling activity.…”

“…Chronic dose among the median-exposed and 5%highly exposed groups were 0.3 and 0.6 g kg -1 day -1 (HQ values ranged from 0.03 to 1 and 1.2 to 2, respectively). Atabila et al (2018b)…”

Pesticide Research on Environmental and Human Exposure and Risks in Sub-Saharan Africa: A Systematic Literature Review

“…Only 18 prospective longitudinal studies exist. Out of the 18, in nine objective exposure [ 25 , 33 , 63 , 97 , 98 , 99 , 100 , 101 , 102 ], in five objective health outcomes [ 25 , 63 , 98 , 99 , 103 ], and in three pesticide dose-response relationship were assessed [ 25 , 63 , 98 ]. Longitudinal studies provide the best quality evidence but are so scarce that it impacts the quality of evidence for contextual decision making and appropriate mitigation of possible risks.…”

Concentrations and temporal trends in pesticide biomarkers in urine of Swedish adolescents, 2000–2017

“…Occupational exposure to pesticides in current use, such as organophosphate insecticides and a few fungicides, has been monitored in agricultural workers in several countries [17][18][19]. Some major general population biomonitoring studies on pesticides are conducted through the National Health and Nutrition Examination Survey in the USA [20][21][22][23][24], the German Environmental Survey [25], and the Canadian Health Measures Survey [3,26].…”