One can assert that with the consumption of a HFCS intensive diet and inadequate Mg intakes, PON1 activity may decrease, along with resulting Ca losses in genetically predisposed individuals. Although there are no human data yet to support this assertion, PON1 activity in rats decreased when fed a HFCS diet to mimic the human metabolic syndrome [39]. PON1 activity has been extensively studied in humans and there are a number of factors known to modulate or alter PON1 expression including, but not limited to, Hg exposure, sex and age [40, 41]. Age plays the most relevant role, as PON1 activity is very low before birth and gradually increases during the first few years of life in humans [41]. In one study, scientists at UC Berkeley found the PON1 levels in many children may remain lower than those of their mothers for several years, especially those with genotypes associated with decreased PON1 activities [42]. The scientists concluded that these children may be more susceptible to OP pesticides throughout their childhood and more vulnerable to conditions associated with oxidative stress such as autism [42]. In a different study, scientists at UC Berkeley found that two-year-old children were less likely to display symptoms of PDD when their mothers had higher paraoxonase levels during their pregnancy [43]. Proper function and adequate expression of the PON1 gene is essential both for prenatal development and child health because exposure to OP pesticides is a common occurrence in the U.S.

The CDC tracks exposure to OP pesticides or their metabolites through the National Biomonitoring Program (NBP). Exposure data are reported for the population as a whole and for subgroups. While most American groups are exposed to OP pesticides, children ages 6 to 11 have significantly higher exposures than adults and are at greatest risk from OP neurotoxicity [44]. Harvard University researchers recently reported finding OP pesticide residues in a number of foods frequently consumed by children [45]. The researchers expressed concern that the children were at times being exposed to multiple pesticide residues in single food commodities. OP pesticide exposures occur primarily from the consumption of foods containing pesticide residues.

It is well known that pesticide exposure can impair neurodevelopment in children, but recent studies have found that pesticide exposure during pregnancy can also cause delayed mental development in children [46]. A review of epidemiological studies in 2008 found that prenatal and childhood exposure to OPs impairs neurobehavioral development [47]. Higher concentrations of urinary dialkyl phosphate (DAP) measured during pregnancy was significantly associated with lower cognitive scores in children at seven years of age. Those children in the highest quintile of maternal DAP concentrations had an IQ score seven points lower than those children in the lowest quintile [48]. In a group of newborns with the highest levels of the organophosphate chlorpyrifos measurable in their umbilical cord blood, birth weight averaged 150 grams less than the group with the lowest exposure [49]. Prenatal pesticide exposure showed deficits consistent with developmental delays of 1.5 to 2 years [49].

Diet is the main source of OP exposure in children. Under the 1996 Food Quality Protection Act, the U.S. Secretary of Agriculture is directed to collect pesticide residue data on commodities frequently consumed by infants and children. USDA Pesticide Data Program (PDP) provides the residue data to comply with this law [50]. We reviewed the PDP data from 2004 to 2008 and identified the foods most frequently found to contain organophosphate insecticide residues. In addition, we obtained the per capita availability data from the USDA to determine the amount of each food commodity the average American consumes [25]. The results of our review indicate that wheat and corn are the commodities most likely contributing to OP exposure in U. S. children. Estimated per capita wheat consumption was approximately 95 pounds per year while estimated per capita corn consumption was approximately 23 pounds per year. The primary use of corn is for the production of corn sweeteners, such as HFCS; however, pesticide residue data were not gathered for this commodity by the PDP. Table 2 provides a complete breakdown of the results of this data review.

Table 2 PDP residue detections by year sampled wi th U.S. per capita consumption data Full size table

From Table 2 it is clear consumers are at risk of exposure to multiple OP pesticide residues from consuming the very same commodity. Cumulative exposures will continue to occur in the U.S. where OP pesticide use is widespread by the agricultural industry. Although OP pesticide use is equally widespread in other countries, there is genetic variation across populations that determine degree of susceptibility to OP exposure. The PON1 gene variants associated with autism in subgroups of the U.S. population but not in Italy could be attributed to the fact that HFCS consumption rarely occurs in Italy, thereby lessening the conditions for PON1 modulation.