Probabilistic assessment of chlorpyrifos exposure to rice farmers in Viet Nam

Abstract

Chlorpyrifos is the most common organophosphate compound registered for agricultural use in Vietnam. The aim of this study was to evaluate chlorpyrifos exposure to rice farmers in Vietnam, using a probabilistic approach. Urine samples on a 24-h basis were collected from farmers before and post application of pesticide. Samples were analysed for 3,5,6-trichloro-2-pyridinol (TCP), the major urinary metabolite of chlorpyrifos, using an enzymatic pre-treatment for extraction and HPLC-MS/MS. Absorbed daily doses (ADD) of chlorpyrifos for farmers were subsequently estimated from the urinary TCP levels. The baseline and postapplication exposure levels were evaluated at the 5th, 50th, and 95th percentile representing low, medium and high-exposure groups in the population. Regression analysis was applied to examine the association between exposure level and factors. The baseline exposure level, which ranged from 0.03 to 1.98 mg/kg/day was below the chronic guidelines recommended by international and national bodies. However, the post-application exposure level, which ranged from 0.35 to 94 mg/kg/day exceeded most of the acute guidelines at the 95th percentile level. Multivariate analysis provided strong evidence for a relationship between post-application exposure level and amount of chlorpyrifos used, as well as body coverage of personal protective equipment.

Assessment of Health Risk in Human Populations Due to Chlorpyrifos

“…An evaluation by Attfield et al [24] into the use of spot sampling indicates that it requires the use of several sample measurements to achieve an accurate evaluation. This approach is supported by the outcomes of our previous research [12,13]. Results from these samples can be compared to the Guideline Values for chronic exposure in Table 1, eg CRfD.…”

“…The ECID with the Thai farmers was probably a reflection of the exposure from various sources including those which occurred during their normal farming activities [41]. However the post application ECIDs were directly related to the chlorpyrifos exposure received from a planned application event [2,13]. In contrast, the Thai farmers exposure was not related to an application event and thus could be expected to be lower [41].…”

“…The exposure levels were found to exceed the acute exposure guidelines of various countries [13]. In addition, the risk was characterised using various probabilistic techniques indicating a health risk [14].…”

“…TCP levels were estimated and the ECIDs were calculated using creatinine adjustment. The baseline exposure levels ranged from 30 to 1980 ng/kg/day while the post application levels were 350 to 94,000 ng/kg/day and the data were plotted as CPDs [13]. Exposure at the 0.95 and the 0.50 levels were reported for the baseline (1600 and 30 ng/kg/day respectively) and the post application situations (11,000 and 680 ng/kg/day respectively) ( Table 3).…”

Chlorpyrifos: pollution and remediation

“…Although its use in certain applications has been restricted in several countries, producers easily find market in most of the developing and non-developing countries. Low economic price and easy access make public choose chlorpyrifos over the other pesticides (Panuwet et al 2009;Lu 2011;MunozQuezada et al 2012;Murphy et al 2012;Phung et al 2012). It was reported as one among the most commonly used organophosphate pesticide in the USA in 2007, with an estimated 7-9 million pounds applied (Grube et al 2011).…”