Abstract
In Chile, agriculture is a relevant economic activity and is concomitant with the use of pesticides to improve the yields. Acute intoxications of agricultural workers occur with some frequency and they must be reported to the surveillance system of the Ministry of Health. However the impacts of chronic and environmental pesticide exposure have been less studied. Among pesticides frequently used in Chile for insects control are organophosphates (OP) and carbamates (CB). They are inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). In this study we determined the pattern of both biomarkers activity in three populations with different type of chronic exposure to OP/CB: environmentally exposed (EE), occupationally exposed (OE) and a reference group (RG) without exposure. Besides this, we also measured the activity of acylpeptide hydrolase (APEH), an enzyme involved in relevant functions in the central synapses that is also expressed in erythrocytes and previously reported to be highly inhibited by some OP. A baseline measurement was done in both exposure groups and then a second measurement was done during the spraying season. The RG was measured only once at any time of the year. Our results indicate that people under chronic OP/CB exposure showed an adaptive response through an increase of basal BChE activity. During the spray season only BChE activity was decreased in the EE and OE groups (p<0.05 and p<0.01, respectively) and the higher magnitude of BChE inhibition was observed in the EE group. The analysis of the frequencies of inhibition above 30% (biological tolerance limit declared by Chilean legislation) indicated that BChE was most frequently inhibited in the EE group (53% of the individuals displayed inhibition) and AChE in the OE group (55% of the individuals displayed AChE inhibition). APEH activity showed the highest frequency of inhibition in the EE group independent of its magnitude (64%). Our results demonstrate that the rural population living nearby agricultural settings displays high levels of environmental exposure. APEH activity seems to be a sensitive biomarker for acute low-level exposure and its usefulness as a routine biomarker must to be explored in future studies. Systematic biomonitoring and health outcomes studies are necessary as well as obtaining the baseline for BChE and AChE activity levels with the aim to improve environmental and occupational health policies in Chile.
Highlights
Pesticides are used worldwide to increase crop and harvest yields, as well as for domestic and public-health related pest control
Sampling was performed by convenience and a questionnaire applied to the volunteers was used for classification in these pre-defined groups: Group 1, the environmentally exposed (EE) group that consisted of individuals living near agricultural land, with no known occupational exposure to organophosphorus pesticides (OP) (n = 66); group 2, the occupationally exposed (OE) group that consisted of agricultural workers who reported continuous and direct contact with pesticides for more than 5 years with no episode of acute poisoning (n = 87); and group 3, a non-exposed reference group (RG) that consisted of people living in Chilean rural or urban coastal areas, far from agricultural settings and with no known exposure to pesticides (n = 100)
Sex was distributed differently among groups (p
Summary
Pesticides are used worldwide to increase crop and harvest yields, as well as for domestic and public-health related pest control. Known as anticholinesterase pesticides, these compounds inhibit the catalytic activity of acetylcholinesterase (AChE), preventing the breakdown of acetylcholine (ACh) at synapses and leading to overstimulation of muscarinic and nicotinic cholinergic receptors [2,3]. Trace amounts of the parent compound in blood, or its metabolites in urine, are used as exposure biomarkers [9] and inhibition of the catalytic activity of erythrocyte AChE is often used as a biomarker of acute OP/CB effects. Butyrylcholinesterase (BChE), a plasma enzyme synthesized in the liver with similar catalytic properties to AChE, is routinely used to determine acute exposure in biomonitoring programs. Reasons to measure BChE instead of AChE activity include its higher degree of reproducibility between laboratories [11,12], and the relative simplicity of isolating plasma from whole blood, wherein the enzyme is found
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