Determination of the genotype and phenotype of serum paraoxonase 1 (PON1) status in a group of agricultural and nonagricultural workers in the Coquimbo Region, Chile

DNA damage in a Chilean population exposed to pesticides and its association with PON1 (Q192R and L55M) susceptibility biomarker

The active ingredients in pesticides are known to be genotoxic that can cause mutations, chromosomal aberrations, or other types of DNA damage. Early detection of genotoxicity reduces the risk of developing diseases such as cancer or suffering from reproductive disorders. In turn, the genotoxic risk depends on the intrinsic capability of the individual to metabolize and eliminate the xenobiotic from the organism. This study aimed to determine if two polymorphisms of paraoxonase-1 (PON1), which is involved in the metabolism of several organophosphate (OP) pesticides, are predictors of susceptibility to DNA damage in agricultural workers and inhabitants of rural areas chronically exposed to pesticides. A cross-sectional study was made considering three groups: agricultural workers (occupational exposure, OE, n = 85), rural inhabitants (environmental exposure, EE, n = 60), and an unexposed group conformed by people living far from agricultural areas (U, n = 33). The level of individual DNA damage was measured using the comet assay, and genotyping was done to determine the PON1 Q192R and L55M polymorphisms. Acetylcholinesterase and butyrilcholinesterase activities were also measured to determine exposure to OP. Individuals belonging to EE and OE groups displayed higher levels of DNA damage compared with U group (p < .001). OP exposure was the main predictor of genotoxicity (β = 16.19; 95% CI: 1.85, 30.52), instead of PON1 polymorphisms (β = -12.20; 95% CI: -27.87, 3.48). These results confirm the genotoxic effects of pesticide exposure and suggest that the catalytic efficiency of PON1 to metabolize OP pesticides becomes negligible in individuals with a history of long-term environmental or occupational exposure to these substances.

Longitudinal exposure to pyrethroids (3-PBA and trans-DCCA) and 2,4-D herbicide in rural schoolchildren of Maule region, Chile

BACKGROUND

Several studies showed that early exposure to pesticides affects the development and health of children. In Maule, there is previous evidence of the high exposure to organophosphate pesticides (OP) of schoolchildren. However, to date, there are no studies assessing exposure to pyrethroids and the herbicide 2,4-D. Objetive. To evaluate children's exposure to pyrethroids insecticides 3-phenoxybenzoic acid (3-PBA), trans 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (trans-DCCA) and 2,4 dichlorophenoxyacetic acid (2,4-D) herbicides.

METHOD

Longitudinal study with 48 schoolchildren from two rural schools in the Maule region, Chile. Urinary metabolites of pyrethroids 3-PBA, Trans-DCCA and 2,4-D herbicides were evaluated in 2016 and 2017. Mann-Whitney U for repeated measurements and Spearman's rho correlation tests were used for data analysis. Also, we used a system of impulsive differential equations for mathematical modeling.

RESULTS

All the schoolchildren assessed had more than two pesticide urinary metabolites in both years, with the 3-PBA metabolite being the most frequent. There was an increase in concentrations of urinary 3-PBA in November 2017, compared to 2016 (from 0.69 μg/L to 1.90 μg/L). In 2016, the specific metabolites of 3-PBA were correlated with Trans-DCCA, 2,4-D, chlorpyrifos, diazinon, and para-nitrophenol. In 2017, 3-PBA was correlated with 2,4-D, and Trans-DCCA. The concentrations of 3-PBA of Chilean children were higher than studies conducted in the USA that found an association of prenatal exposure to these metabolites with cognitive difficulties.

CONCLUSIONS

We found high concentrations of pyrethroid metabolites among all the schoolchildren assessed, which may impact on their health and development. These insecticides had received no attention from the scientific community in Chile, and neither from the government agencies, despite the increased use of these chemicals in recent years. This is the first study in South America that confirms the exposure to pyrethroids and herbicides through biomarkers in human population living near farm fields.

Pesticide application, educational treatment and infectious respiratory diseases: A mechanistic model with two impulsive controls

In this paper, we develop and analyze an SIS-type epidemiological-mathematical model of the interaction between pesticide use and infectious respiratory disease transmission for investigating the impact of pesticide intoxication on the spread of these types of diseases. We further investigate the role of educational treatment for appropriate pesticide use on the transmission dynamics. Two impulsive control events are proposed: pesticide use and educational treatment. From the proposed model, it was obtained that the rate of forgetfulness towards educational treatment is a determining factor for the reduction of intoxicated people, as well as for the reduction of costs associated with educational interventions. To get reduced intoxications, the population’s fraction to which is necessary to apply the educational treatment depends on its individual effectiveness level and the educational treatments’ forgetfulness rate. In addition, the turnover of agricultural workers plays a fundamental role in the dynamics of agrotoxic use, particularly in the application of educational treatment. For illustration, a flu-like disease with a basic reproductive number below the epidemic threshold of 1.0 is shown can acquire epidemic potential in a population at risk of pesticide exposure. Hence, our findings suggest that educational treatment targeting pesticide exposure is an effective tool to reduce the transmission rate of an infectious respiratory disease in a population exposed to the toxic substance.

[Pesticide exposure in Chile and population health: urgency for decision making]

In the last 25 years, Chile has had an expanding role as an agro-export country in the global economy, with efficient rates of productivity in the region, based on the technological development of agriculture, with of large monocultures whose productivity depends on the intensive application of agrochemicals. This form of agriculture has also lacked efficient regulations and surveillance, so it is difficult to estimate the real magnitude of the exposed population and its effects on health in the short or long term. This systematic review compiles the epidemiological evidence generated from studies conducted in several regions of Chile regarding pesticide exposure and health effects. Of the total number of articles, 50% included agricultural workers, 25% children, and 25% women of childbearing age, with the greatest effects being the neurotoxic (54%), genotoxic (31%) and reproductive (15%). The evidence collected shows that in Chile the levels of exposure to pesticides in the general and occupational population are higher than international studies levels. It is urgent to protect the health of both the occupational and general population and especially children through a stricter control of the sale and use of pesticides, with comprehensive surveillance systems in environmental health and educational actions in the social and cultural context of rural communities. It is a priority to strengthen research with national relevance on health effects, and strictly restrict the use of pesticides already prohibited in developed countries due to their high level of risk to human and environmental health.

Association between cholinesterase's inhibition and cognitive impairment: A basis for prevention policies of environmental pollution by organophosphate and carbamate pesticides in Chile

BACKGROUND

In Chile organophosphate pesticides are widely used in the production of fruits. Pesticides use is regulated for professional practice but there is no regulation regarding exposure to the general population.

OBJECTIVE

To relate exposure to cholinesterase's inhibitor pesticides during the spray season with neuropsychological impairment in occupationally exposed (OE) and environmentally exposed (EE) groups of people.

METHODS

Exposure was assessed through inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity and neuropsychological outcomes were evaluated through a large battery of tests covering general mental status, language, memory, attention, executive function, praxis and psychomotricity. Evaluations were carried out firstly in a period of no/low organophosphate pesticide use and subsequently during the spray season. All parameters were calculated as the relative change from baseline to spray season.

RESULTS

For this study in total 156 participants were recruited divided equally over participants with environmental exposures (EE) and participants with occupational exposure (OE). In the EE, BChE's enzyme activity inhibition ≥30% showed significant association with 10% or more decreased performance in several tests evaluating six of the eight cognitive areas (excepting psychomotricity and mood status); besides, for AChE inhibition in EE, the association was significant in three tests evaluating attention and one of executive function. Whereas, in OE, the inhibition of the BChE ≥30% was associated with a low performance of one attention test and for AChE the exceedance of the standard was associated with diminished performance in one test of memory and attention, respectively. The association between biomarkers of biological effect and cognitive impairment persisted among the EE group after removing confounders. No association was found between biomarkers of biological acute effect and decreased cognitive performance in the OE group.

CONCLUSIONS

Increased exposure to pesticides was confirmed by increased inhibition of cholinesterase's in both exposure groups; which was associated with a diminished neuropsychological performance, mainly in the environmentally exposed study group. [310 words].

Susceptibility to organophosphates pesticides and the development of infectious-contagious respiratory diseases

In this paper we develop an SIRS compartmental model to investigate the dynamic interplay between pesticide intoxication and the spread of infectious-contagious respiratory diseases. We are particularly interested in investigating three levels of genetic susceptibility to pesticide intoxication. The genotypic distribution of susceptibility to pesticide intoxication, is proposed and parameterized according to ethnic variation using real population data from published studies, and we assume that pesticide intoxication increases susceptibility to infection with a respiratory pathogen. We use mathematical models to illustrate the impact of this distribution on the spread of hypothetical respiratory disease in a population exposed to the organophosphate pesticide. In this context, we show how an initial basic reproductive number below the epidemic threshold of 1.0 could be enhanced to support epidemic outbreaks in agricultural populations that employ chlorpyrifos pesticides. We further illustrate our modeling framework to study the effect of ethnic group variation in Singapore (Malay, Indian and Chinese) using genetic distribution data from published studies.

Biomarkers of oxidative stress in blood of workers exposed to non-cholinesterase inhibiting pesticides

In occupational settings workers are often exposed to pesticides at relatively high doses compared to environmental exposures. Long-term exposure to pesticides has been associated with numerous adverse health effects in epidemiological studies, and oxidative stress is often claimed as one of the underlying mechanisms. In fact, different pesticides have been reported to induce oxidative stress due to the generation of free radicals and/or alteration in antioxidant defense enzymes. The present study examined greenhouse workers regularly exposed to diverse pesticides under integrated production system, and a group of controls of the same geographic area without any chemical exposure. Two different periods of the same crop season were assessed, one of high exposure (with greater use of pesticides) and other of low exposure (in which a less use of these compounds was made). Non-specific biomarkers of oxidative stress, e.g. thiobarbituric acid reactive substances (TBARS), ferric reducing ability of serum (FRAS), total thiol groups (SHT), gamma-glutamyl transpeptidase (GGT) and paraoxonase-1 (PON1) were measured in serum samples from all study subjects, alongside erythrocyte acetylcholinesterase (AChE). Results are suggestive of a mild increase in oxidative stress associated with pesticide exposure, which was compensated by an adaptive response to raise the antioxidant defenses and thus counter the detrimental effects of sustained oxidative stress. This response led to significantly increased levels of FRAS, SHT and PON1 in greenhouse workers relative to controls. Furthermore, AChE was decreased likely as a result of oxidative stress as workers did not use organophosphate insecticides.

Paraoxonase-1 genetic polymorphisms in organophosphate metabolism

Organophosphates (OPs) are a class of chemicals commonly used in agriculture as pesticides, that can often lead to severe toxicity in humans. Paraoxonase-1 (PON1) belongs to a family of A-esterases and hydrolyses several OPs while also serving other biological roles. Two main genetic polymorphisms have been shown to affect enzymatic ability; an A > G transition in the 192nd position (192 Q/R, rs662), and an A > T at codon 55 (55 M/L, rs854560). In this review, we searched PubMed for relevant articles published from its inception till June 2018 and included publications from 1996 to 2018. We aimed to address the distribution of the polymorphisms in various populations, the way they affect enzymatic activity and the possible use of PON1 as a biomarker. The polymorphisms present great heterogeneity between populations, with the data being clearer over 192 Q/R, and this heterogeneity is related to the phylogenetic origins of each population. Concerning enzymatic activity, the different genotypes react better or worse to different OP substrates, with studies presenting a variety of findings. Detecting the "paraoxonase status" of an individual -referring to PON1 function- seems to be important in predicting OP toxicity, as studies have shown that some specific-genotype individuals present symptoms of toxicity in higher rates than others. We are strongly convinced that in order for the scientific community to reach a consensus over which polymorphisms confer susceptibility to toxicity and whether PON1 can eventually be used as a biomarker, more studies need to be carried out, since the data thus far does not seem to reach a universal conclusion.

Biomonitoring of blood cholinesterases and acylpeptide hydrolase activities in rural inhabitants exposed to pesticides in the Coquimbo Region of Chile

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.