Organophosphate insecticide exposure and respiratory symptoms among school children in Northern Thailand: Interaction by biomass burning, dampness and season.

ABSTRACT

The aim was to study associations between dialkylphosphates (DAPs), organophosphate (OP) metabolites in urine, biomarkers of OP insecticide exposure, and respiratory symptoms among children in upper northern Thailand. We recruited junior high school children in randomly selected schools in four cities (N = 337), with repeated data collection in wet and dry seasons. Urine was collected and analyzed for six OP metabolites, with creatinine adjustment. Total DAP was expressed as sum of DAPs. Data on respiratory symptoms was collected by a standardized questionnaire. Associations were analyzed by multiple logistic regression. Totally 11.3 % lived in farm families. Total DAPs concentration was higher in dry season (p = 0.002) but did not differ between farm and non-farm children. Total DAPs in wet season was associated with current wheeze (p = 0.019), current asthma attacks (p = 0.012) and attacks of breathlessness in last 12 months (p = 0.021). Total DAPs in dry season was associated with current wheeze (p = 0.042), and associations between DAPs and respiratory symptoms were stronger for dimethylphosphate metabolites (DMPs) than for diethylphosphate metabolites (DEPs). DMPs are produced by certain OP pesticides. Biomass burning inside or outside the home, and dampness or mold at home, enhanced the association between total DAPs and attacks of breathlessness. In conclusion, OP pesticide exposure, measured as urinary DAPs, was higher in dry season and similar in farm and non-farm children. OPs exposure, especially to DMP related pesticides, can increase asthmatic symptoms, especially in wet season. Combined exposure to OP and smoke from biomass burning, or dampness and mold, can further increase the prevalence of attacks of breathlessness. There is a need to reduce OP insecticide and biomass smoke exposure among Thai children. Since different pesticides can be used in different seasons, studies on respiratory health effects of OPs pesticide exposure should be done in different seasons.