Children can be exposed to organophosphate and carbamate mixtures, which pose additive health effects via soil exposure. However, only 23 countries have soil standard values for organophosphate and carbamate pesticides, and most regulatory jurisdictions do not consider the cumulative exposure. This study derived proposed soil standards for organophosphates and carbamates by introducing the relative potency quotient approach (RPQ). The probabilistic cumulative risk assessment was also applied to evaluate current soil standards of pesticide mixtures. The U.S. Environmental Protection Agency (EPA) have soil standards of 19 organophosphates and five carbamates. However, these standards cannot protect population health via chronic exposure in conservative and semi-conservative scenarios based on the probabilistic risk assessment because the U.S.EPA simplified the regulatory process for the cumulative exposure to pesticide mixtures and omitted the soil allocation factor, which should be set for aggregate exposure. The analysis of proposed soil standards developed by the RPQ approach indicates that some human behavior variables, such as soil intake rate and exposure duration, have stronger impacts on the proposed soil standards than human biometric variables like body weight. This study may be helpful to develop regulatory standards and a framework for pesticide mixtures having additive health effects.

The study was prompted to characterize the B-type esterase activities in the terrestrial snail Xeropicta derbentina and to evaluate its sensitivity to organophosphorus and carbamate pesticides. Specific cholinesterase and carboxylesterase activities were mainly obtained with acetylthiocholine (Km = 77.2 mM; Vmax = 38.2 mU/mg protein) and 1-naphthyl acetate (Km = 222 mM, Vmax = 1095 mU/mg protein) substrates, respectively. Acetylcholinesterase activity was concentration-dependently inhibited by chlorpyrifos-oxon, dichlorvos, carbaryl and carbofuran (IC50 = 1.35 x 10-5-3.80 x 10-8 M). The organophosphate-inhibited acetylcholinesterase activity was reactivated in the presence of pyridine-2-aldoxime methochloride. Carboxylesterase activity was inhibited by organophosphorus insecticides (IC50 = 1.20 x 10-5-2.98 x 10-8 M) but not by carbamates. B-esterase-specific differences in the inhibition by organophosphates and carbamates are discussed with respect to the buffering capacity of the carboxylesterase to reduce pesticide toxicity. These results suggest that B-type esterases in X. derbentina are suitable biomarkers of pesticide exposure and that this snail could be used as sentinel species in field monitoring of Mediterranean climate regions. Characterization of the B-type esterases in the terrestrial snail Xeropicta derbentina in order to evaluate pesticide exposure.

Marine bivalves such as oysters are widely used as bioindicators to monitor marine coastal pollution. This study aimed to use B-esterase activity responses in oysters (Crassostrea gigas) cultured in Ebro Delta bays to monitor environmental effects of pesticides. The B esterases investigated were acetylcholinesterase, propionylcholinesterase, and carboxylesterase and their activities were measured in adductor muscle and gills from oysters transplanted in Ebro Delta bays where the are traditionally grown. Enzyme activities were related with physico-chemical parameters and pesticide levels measured in water. Cholinesterase activities measured in gills were unaffected across sites and periods. Conversely, carboxylesterase activities in oyster gills varied across periods and sites and were negatively correlated with residue levels of organophoshporous and carbamate pesticides in water. Therefore, inhibition of carboxylesterase activities can be considered a good indicator of exposure to anti-cholinergic pesticides in oysters.

Organophosphate and carbamate pesticides have been widely used by farmers for crop protection and pest control. Inhibition of acetylcholinesterase (AChE) in erythrocyte and butyrylcholinesterase (BChE) in plasma is the predominant toxic effect of organophosphate and carbamate pesticides. Mae Taeng District, Chiang Mai Province, is one of the large areas of growing vegetables and fruits. Due to their regular exposure to these pesticides, the farmers are affected by this toxicity. The objective of the study was to examine the AChE and the BChE activity levels in the blood of 102 farmers for comparison of exposure in two cropping seasons, winter and hot. Blood samples were collected in December 2013 (winter) and April–June 2014 (hot). A total of 102 farmers joined the study, represented by 76 males (74.5 %) and 26 females (25.5 %). The age of most of the farmers was 53.4 ± 8.7 years. Out of 102, 21 farmers used carbamate pesticides. The results showed that the AChE and the BChE activity levels of all the farmers were 3.27 ± 0.84 Unit/mL and 2.15 ± 0.58 Unit/mL, respectively. The AChE and the BChE activity levels in males were 3.31 ± 0.88 Unit/mL and 1.97 ± 0.60 U/mL, respectively, during winter and 3.27 ± 0.82 Unit/mL and 2.15 ± 0.58 U/mL, respectively, during the hot season, and AChE and the BChE activity levels in females were 3.27 ± 0.82 U/mL and 2.44 ± 0.56 U/mL, respectively, during the hot season. The cholinesterase activity levels, both AChE and BChE, in the male farmers’ blood had significant difference between the two seasons, while in the case of the female farmers, there was significant difference in the BChE activity levels, at p < 0.05. The BChE activity level was found to significantly correlate with self-spray (p < 0.05), which implies that the BChE activity decreased when they sprayed by themselves. The cholinesterase activity levels of the present study were lower than those of the other studies, which may be an indication of some chronic effect of exposure to anticholinesterase pesticides. Thus, it is recommended that the use of pesticides be decreased, together with increase in the awareness of the impact of pesticides on health; also recommended is regular monitoring of blood cholinesterase.

Acetylcholinesterase (AChE) acts on the hydrolysis of acetylcholine, rapidly removing this neurotransmitter at cholinergic synapses and neuromuscular junctions as well as in neuronal growth and differentiation, modulation of cell adhesion (“electrotactins”) and aryl-acylamidase activity (AAA). This enzyme is also found in erythrocyte, as 160 kDa dimer that anchors to the plasma membrane via glycophosphatidylinositol. The function of this enzyme in erythrocytes has not yet been elucidated; however, it is suspected to participate in cell-to-cell interactions. Here, a review on erythrocyte AChE characteristics and use as biomarker for organophosphorus and carbamate insecticides is presented since it is the first specific target/barrier of the action of these pesticides, besides plasma butyrylcholinesterase (BChE). However, some past and current methods have disadvantages: (a) not discriminating the activities of AChE and BChE; (b) low accuracy due to interference of hemoglobin in whole blood samples. On the other hand, extraction methods of hemoglobin-free erythrocyte AChE allows: (a) the freezing and transporting of samples; (b) samples free of colorimetric interference; (c) data from only erythrocyte AChE activity; (d) erythrocyte AChE specific activity presents higher correlation with the central nervous system AChE than other peripheral ChEs; (e) slow spontaneous regeneration against anti-ChEs agents of AChE in comparison to BChE, thus increasing the chances of detecting such compounds following longer interval after exposure. As monitoring perspectives, hemoglobin-free methodologies may be promising alternatives to assess the degree of exposure since they are not influenced by this interfering agent.

The immune system can be the target of many chemicals, with potentially severe adverse effects on the host’s health. In the literature, carbamate (CM) pesticides have been implicated in the increasing prevalence of diseases associated with alterations of the immune response, such as hypersensitivity reactions, some autoimmune diseases and cancers. CMs may initiate, facilitate, or exacerbate pathological immune processes, resulting in immunotoxicity by induction of mutations in genes coding for immunoregulatory factors and modifying immune tolerance. In the present study, direct immunotoxicity, endocrine disruption and inhibition of esterases activities have been introduced as the main mechanisms of CMs-induced immune dysregulation. Moreover, the evidence on the relationship between CM pesticide exposure, dysregulation of the immune system and predisposition to different types of cancers, allergies, autoimmune and infectious diseases is criticized. In addition, in this review, we will discuss the relationship between immunotoxicity and cancer, and the advances made toward understanding the basis of cancer immune evasion.