PON1 status does not influence cholinesterase activity in Egyptian agricultural workers exposed to chlorpyrifos

Abstract

Animal studies have shown that paraoxonase 1 (PON1) genotype can influence susceptibility to the organophosphorus pesticide chlorpyrifos (CPF). However, Monte Carlo analysis suggests that PON1 genotype may not affect CPF-related toxicity at low exposure conditions in humans. The current study sought to determine the influence of PON1 genotype on the activity of blood cholinesterase as well as the effect of CPF exposure on serum PON1 in workers occupationally exposed to CPF. Saliva, blood and urine were collected from agricultural workers (n = 120) from Egypt’s Menoufia Governorate to determine PON1 genotype, blood cholinesterase activity, serum PON1 activity towards chlorpyrifos-oxon (CPOase) and paraoxon (POase), and urinary levels of the CPF metabolite 3,5,6-trichloro-2-pyridinol (TCPy). The PON1 55 (p ≤ 0.05) but not the PON1 192 genotype had a significant effect on CPOase activity. However, both the PON1 55 (p ≤ 0.05) and PON1 192 (p ≤ 0.001) genotype had a significant effect on POase activity. Workers had significantly inhibited AChE and BuChE after CPF application; however, neither CPOase activity nor POase activity was associated with ChE depression when adjusted for CPF exposure (as determined by urinary TCPy levels) and stratified by PON1 genotype. CPOase and POase activity were also generally unaffected by CPF exposure although there were alterations in activity within specific genotype groups. Together, these results suggest that workers retained the capacity to detoxify chlorpyrifos-oxon under the exposure conditions experienced by this study population regardless of PON1 genotype and activity and that effects of CPF exposure on PON1 activity are minimal.

Paraoxonase activity and genetic polymorphisms in northern Han Chinese workers exposed to organophosphate pesticides

“…However, there was no significant contribution of other predictors considered in this study to enzyme activity. Although ChE activity is a important parameter to reflect OP exposure, there was no significant contribution of ChE activity to PON1 activities, which is in line with the results from Ellison et al 40 So far there are some investigations of the association between PON1 polymorphisms and risk of diseases (such as coronary heart disease, diabetes mellitus and cerebral infarction) in the Chinese population, [41][42][43] but there is little information on PON1 activity and the association between PON1 status and sensitivity to OP toxicity in the Chinese population who are occupationally exposed to pesticides. Our current investigation might be the first study to show an association between PON1 polymorphisms and susceptibility to OP toxicity in China.…”

Characterizing exposures and neurobehavioral performance in Egyptian adolescent pesticide applicators

“…Therefore, in the case of a single applicator and non-applicator, there's an 86.6 % (95 % CI: 75.0–98.3 %) chance the applicator would have a higher TCPy concentration. Figure 1 shows that the average TCPy levels for adolescent applicators and non-applicators in the current study are similar to those found for adult pesticide applicators and non-applicators from the same region in August 2009 (adult data from, Ellison et al 2012). The Egyptian applicators and non-applicators had much higher urinary TCPy levels than the geometric mean for adolescents (12–19 years) reported in National Health and Nutrition Examination Survey (Centers for Disease Control and Prevention 2009).…”

“…Additional research in this adolescent population provides further evidence of environmental exposure; an increase in TCPy levels, above baseline, was found in both applicator and non-applicator groups during the application season, with a significantly greater increase in the applicator population (Crane et al 2013). Although elevated levels were found in the adolescent applicators compared to the non-applicators, they are similar to the levels reported in adult pesticide workers in Egypt in August 2009 (Ellison et al 2012), but are markedly less than observed in adult applicators in 2008 (Farahat et al 2011). The variability in occupational exposures observed in adult applicators in part reflects the year-to-year variation in the use of pesticides on cotton fields.…”

“…These environmental factors may have contributed to the elevated exposures seen in the non-applicator participants and may have potentially confounded the neurobehavioral outcomes. Although TCPy levels in applicators are elevated compared to the non-applicators and other adult applicator groups from the US (CDC 2009), their levels are similar to or less than reported in adult pesticide applicators in Egypt (Ellison et al 2012; Farahat et al 2010, 2011). …”

“…Average TCPy levels for adolescent applicators and non-applicators in the current study and for adult pesticide applicators and non-applicators from the same region in August 2009 (Ellison et al 2012). Dotted line indicates geometric mean for adolescents (12–19 years) reported in National Health and Nutrition Study (Centers for Disease Control and Prevention 2009)…”