Council on Environmental Health
Article Review

Prepared by: James R. Roberts, MD, MPH
May 2008

TITLE
Dietary Intake and its Contribution to Longitudinal Organophosphorus Pesticide Exposure in Urban/Suburban Children

AUTHORS
Chensheng Lu, Dana B. Barr, Melanie A. Pearson, and Lance A. Waller

REFERENCE
Environmental Health Perspectives 2008;116(4):537-42

STUDY DESIGN
Prospective with dietary intervention

BACKGROUND
Organophosphate insecticides (OP) are known to be acutely toxic and epidemiologic data exists to link the exposure of high levels of OPs with neurological effects.  The effects of lower levels and chronic exposure to OPs are less understood. One reason for this is the limited data that clearly define what long term exposure really is and the sources of the OP exposure.

METHODS
The authors recruited children in the 3-11 year age group and followed them at regular intervals for one year.  Prior to consent into the study, families were pre-interviewed to determine eligibility for the study. Questions included whether they were on conventional diets (non-organic) and whether caregivers were willing and able to participate in the study’s strict protocol involving numerous urinary collections, regular collection of dietary information, and substitution of organic foods for short consecutive periods in the summer and fall. Once enrolled in the study, urinary samples were collected during 15 and 12 day sampling periods in the summer and fall respectively, as well as 7 day sampling periods in the winter and spring.  The organic food was substituted during 5-day periods in both the summer and fall seasons based on the family’s usual dietary intake.  Specific urinary metabolites for chlorpyrifos, malathion, diazinon, coumaphos, and methyl pirimiphos were measured in urine and saliva. Data were analyzed using a linear mixed-effects model in SPSS 13 with repeated urinary measurements for each participant.

RESULTS
Twenty-three children were enrolled and have at least summer urinary metabolite data with complete 12- month data being collected for 19 children.  Chlorpyrifos and malathion were the two metabolites found with the highest frequency of detection and were the two that underwent longitudinal analysis during this study.  Pesticide levels were highest in the spring and summer.  The authors noted an immediate decline in chlorpyrifos and malathion metabolite levels on the first day of the switch to organic diets from conventional diets, and in fact an elimination of malathion metabolites.  Upon the resumption of the convention diet, the urinary metabolites returned to the levels observed prior to the switch to organic foods.  There was a lack of residential use of OP pesticides in this study. In the linear mixed-effects model, season was the only contributor to the urinary metabolite levels. Although not statistically significant, the children consumed more fruit, juices, and vegetables during the summer season. They also consumed the least amount of fresh fruits and vegetables in the fall, which corresponded to the lowest levels of urinary metabolites.

DISCUSSION
This is one of the first studies that focus on suburban and urban children as opposed to children living in an agricultural environment.  Given the lack of pesticide use in the home, it appears likely that in these children, dietary intake is the primary source of pesticides. However, the authors do not discuss the amount of pesticide use in the school grounds.  The authors do note that although they have sampled from a population of children in suburban/urban areas, there was a selection process involved that deemed many families ineligible. This, and the small study sample, indicates that these results may not be generalizable, and should be repeated in other settings. The decline in urinary metabolites during the intervention phases with organic foods however, is intriguing and the decline also appears to mirror the reported biological half life of both malathion and chlorpyrifos.

BOTTOM LINE
This study provides evidence that support the notion that “dietary intake of pesticides represents the major source of exposure for infants and children”, as outlined in the National Research Council’s 1993 report entitled Pesticides in the Diets of Infants and Children.  It also demonstrates an interesting finding that a change to an organic diet (that was tested to ensure a lack of pesticide residues) substantially decreased or even eliminated pesticide residues in the children’s urine.

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