L. Curl, CL , RA Fenske and K Elgethun. 2003. Organophosphorus
pesticide exposure of urban and suburban pre-school children with
organic and conventional diets. Environmental
it might seem obvious that eating organic food reduces exposure
to pesticides, it's rarely been tested directly, particularly in
looking not just what's on the food but what gets into a
child's body because of what they eat.
new study from Seattle reports that school children eating conventionally-grown
fruits and vegetables are more likely to exceed EPA safety
thresholds for organophosphate pesticides than children
eating organic produce. Simple choices by parents can have a
big impact on pesticide exposures.
debate the adequacy of those standards—some saying they are
too lax, others (usually from industry) saying they are too strong.
Whoever is right, this study shows that choosing organic
lowers the chance that thresholds will be exceeded, therefore
making some of the plausible health impacts of exposure to organophosphates
did they do? Curl et al. recruited children for
participation in the studies by interviewing parents entering one
of two grocery stories in the Seattle area, one specializing in
organic, the other not. The scientists then visited the homes of
recruited children twice, on the first visit to interview the parents
about a range of variables including frequency of household pesticide
use, to instruct them in the creation of a "food diary"
so that records would be available to assess the amounts of produce
of different types consumed; and on the second visit to obtain urine
samples were analyzed for the dialkylphosphate metabolites of organophosphate
did they find? After analysis of the food diaries, Curl et al. determined
that 18 of the recruited children ate organic diets, while 21 ate
conventional. Preliminary analysis revealed that the organic and
conventional groups did not differ in gender or age composition
(mean ages were 46 (organic) and 47 (conventional) months. Variables
such as home ownership status and income also did not differ, nor
measurements of the children's activities.
there were overall differences between the conventional vs. organic
families in likelihood of pesticide use around the home (conventional
families more likely), there was no significant difference in frequency
of organophosphate pesticide use.
five dialkylphosphate metabolites measured, dimethylthiophosphate
(DMTP), one was by far dominant over others. DMTP was found in the
urine of 87% of children measured.
heart of the analysis shows that DMTP levels in children eating
organic foods were significantly lower than those eating conventional
the traces of a organophosphate metabolite in the urine of
children eating organic vs. conventional produce.
values averaged 9 times higher in children eating a conventional
a nonparametric statistical test this difference is highly
significant (p < 0.003).
et al. were interested in determining which organophosphate
pesticides were likely to be contributing to these differences:
which ones are used on fruits and vegetables and, when metabolized,
yield DMTP. Through an analysis of EPA records they found that most
OPs are used in ways that would not result in contamination of produce.
Of those used on produce that yield DMTP, oxydemeton-methyl, azinphosmethyl,
phosmet and malathion have the highest annual use on fresh fruits
and vegetables, making them the most likely sources for the contamination
an ideal world, Curly et al. would have been able to collect
precise duplicates of the diets of the children as they were eating,
and analyze those samples to find out what the actual exposures
were that lead to the observed levels of DMTP in urine. This wasn't
possible. They used a clever set of calculations to take a stab
at answering that question.
calculated how much of the four OP pesticides they identified above
would each child have had to have consumed to yield the DMTP levels
they observed. They then looked how often that consumption would
have created exposures exceeding EPA standards.
standards are based on exposure levels (concentrations on food),
not amounts measured in urine. This calculation requires a series
simplifying assumption and also that each compound be treated one-by-one.
In other words, if (for example) malathion is a child's only source
of OP, how much malathion would the child need to be exposed to
to produce that much urinary DMTP? And looking across all the children
they studied, what percentage of those malathion exposures would
violate EPA standards.
found that children eating conventional foods are much more likely
to be exposed to OP levels above the EPA standards. The
results depended upon the compound. The largest difference was seen
for azinphosmethyl: only one child with an organic diet (6%) compared
to eleven children with conventional diets (52%) would exceed the
standard. If all exposure were from oxydemeton-methyl, 88% of the
children with organic diets and 100% of the children with conventional
diets would exceed the EPA standard. For malathion, none would exceed.
does this mean? According to the authors:
study demonstrates that dietary choice can have a significant
effect on children’s pesticide exposure. To our knowledge,
no other studies have tested this hypothesis. Our finding that
children who consume primarily organic produce exhibit lower
pesticide metabolite levels in their urine than children who
consume conventional produce is consistent with known agricultural
practice, since organic foods are grown without pesticides.
Consumption of organic produce represents a relatively simple
means for parents to reduce their children’s pesticide