You are here:
Salivary cholinesterase activity in children with organic and convential diets
Citation:
Henn, B. C., S. T. Argao, S. B. MCMASTER, AND S. J. PADILLA. Salivary cholinesterase activity in children with organic and convential diets. Presented at International Society for Environmental Epidemiology Annual Conference, Pasadena, CA, October 12 - 14, 2008.
Impact/Purpose:
research results
Description:
Objective: Previous efforts to determine the health effects of pesticides have focused on quantifying acetylcholinesterase activity in blood. However, since blood draws can be difficult in young children, saliva biomonitoring has recently been explored as a feasible alternative. In animal studies, organophosphate pesticides have been shown to produce a concentration-related inhibition of salivary cholinesterase activity, which mirrors the decline in blood cholinesterase activity. Human saliva also contains low levels of cholinesterase activity, though little is known about activity in children under 4 years old. This pilot study examined the feasibility of collecting saliva from young children, and assessed whether cholinesterase activity is measurable in children’s saliva. We also explored whether differences in pesticide exposure from organic and conventional diets can be detected in salivary cholinesterase (ChE) activity. Materials and Methods: We collected two saliva samples, one week apart, from 40 children between 2 and 5 years old. Unstimulated whole saliva was collected either by (1) having the child spit into a plastic cup, or (2) manually pipetting saliva from the child’s mouth with a polyethylene Pasteur pipette. Total salivary ChE activity was measured using a modified radiometric assay and normalized for protein content. Daily food diaries were maintained for the week between sampling to verify that children were consuming either mostly conventional or mostly organic diets. Total volume of food consumed was determined and used to calculate percent of diet that was organic. Results: Both saliva collection methods were successful in collecting 1 to 2 ml saliva. Older children (mean age 4.3 yrs) preferred spitting into a cup, while younger children (mean age 3.1 yrs) preferred the pipette method (p<0.01). Total ChE activity was measurable in all samples, with a 2.5% average difference between duplicate saliva samples. Median ChE activity among all children was 27.4 (range 2.9-157.8) nmol hydrolyzed/hr/mg protein. No difference was found in ChE activity between first and second saliva samples (repeated measures, log-transformed ChE, p=0.27). However, there was substantial intra-individual variability (mean coefficient of variation 40%, range 1-84%). Thirteen children were identified by parents as consuming at least 75% organic food. After adjusting for age, ChE activity in these children was similar to activity in children who were identified as mainly conventional consumers (p=0.64). Data from food diaries, however, suggest that most subjects overestimated the percentage of organic food consumed. After reclassifying children based on food diary data, age-adjusted ChE activity was unexpectedly lower among organic consumers compared to conventional consumers (log-transformed ChE, n=28, beta=-1.2, SE=0.52, p=0.03). Further adjustment for gender, home pesticide use, pets, and para-occupational pesticide exposure did not change results. Conclusions: Saliva collection is feasible in young children, though efficiency of the collection method depends on the child’s saliva production and cooperation. Cholinesterase activity is measurable in children’s saliva with good repeatability between duplicate samples. However, the large amount of within-subject variability in the general population may preclude its use as a reliable and sensitive biomarker for low-level pesticide exposure. This abstract is of a proposed presentation and does not necessarily reflect EPA policy.