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The Center’s research is focused on four core areas of
investigation. Below are the findings for each area:
- CHAMACOS Cohort Study
- Pregnant women in the UC-Berkeley study showed higher OP
urinary metabolite levels than women of child-bearing age who
participated in the National Health and Nutrition Examination
Survey (NHANES). Levels in samples collected in the postpartum
period were about twice as high as levels during pregnancy. Researchers
hypothesize that significant changes in maternal physiology after
giving birth may affect the internal distribution of pesticides
and other toxicants
(Bradman et al. 2005).
- Judged against EPA cumulative risk assessment guidelines for OPs,
about 15% of pregnant women participating in the CHAMACOS may
have cumulative OP pesticide exposures exceeding the health protective
reference value
(Castorina et al. 2003).
- DDT and DDE levels were significantly higher in pregnant
CHAMACOS women compared to U.S. national reference data. Women
who were born in coastal Mexico, where DDT was used for agriculture
and malaria control until the year 2000, had much higher levels compared
to women born in central Mexico or the United States
(Bradman et al. 2006).
- Housing quality was very poor in the homes of CHAMACOS participants.
We found a high prevalence of cockroach and rodent infestations, mold,
peeling paint, water damage, etc. Homes with higher levels of disrepair
had higher rates of pest infestations. Compared to a national survey by
HUD, CHAMACOS participants were more likely to have rodents, peeling paint,
leaks under sinks. Housing density was substantially higher in participant homes
than in average homes nationwide, with many households sheltering more
than 1.5 people per room. Pesticides were stored or used in about 50% of households
(Bradman et al. 2005).
- Higher levels of organophosphate (OP) pesticide metabolites in
maternal urine during pregnancy were associated with shorter gestational
duration. A ten-fold increase in average dimethyl, but not diethyl,
phosphate metabolites was associated with a decrease of three days in
gestational duration (p=0.02). Lower levels of acetyl cholinesterase
(suggesting higher OP exposure) in umbilical cord blood were also
associated with significantly shorter length of gestation. No adverse
associations were found between OP exposure and infant birth weight,
length, or head circumference
(Eskenazi et al. 2004).
- Researchers found that hexachlorobenzene was associated with
decreased length of gestation. No effect was seen on birth weight
or length. No significant associations were found with any other
organochlorine analyzed, including DDT and DDE.
(Fenster et al. 2006).
- Neonates whose mothers had higher OP pesticide metabolite levels
during pregnancy were more likely to have abnormal reflexes in the
neonatal period as assessed by the Brazelton Neonatal Behavioral
Assessment Scale (BNBAS). OP exposure was associated with both an
increase in number of abnormal reflexes and with the proportion of infants
with more than three abnormal reflexes. No detrimental associations
were found with other BNBAS clusters
(Young et al. 2005).
- Higher levels of OP pesticide metabolites during pregnancy
were also associated with poorer mental development at age
24 months. Although prenatal exposure was negatively associated
with mental development, postnatal exposure appeared to be positively
associated, for reasons not yet understood. Higher OP metabolite levels in both the prenatal and
postnatal periods were associated with increased risk of pervasive
developmental disorder
(Eskenazi et al. 2007).
- UC Berkeley Center researchers also found a negative association
between maternal DDT levels during pregnancy and child mental development
at 24 months. Each ten-fold increase in DDT level was associated with
a 2- to 3-point decrease in mental development, corresponding to a 7-
to 10-point decrease across the range of exposure of the population
(Eskenazi et al. 2006).
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- CHAMACOS Intervention Studies
- Wearing coveralls reduced pesticide residues on regular
work clothing (Bradman et al. in preparation)
- Leaving coveralls at work reduced the potential for take-home
pesticide exposure (Bradman et al. in preparation)
- Workers who wore gloves had significantly lower amounts of
pesticides on their hands and in their urine (Bradman et al.
in preparation)
- Worker who ate strawberries directly from the fields had higher
levels of pesticides in their urine than those who did not (Bradman
et al. in preparation)
- Workers were very positive about the coveralls and gloves.
They felt they did not hamper productivity. Approximately 85% of
workers said they would always wear coveralls and gloves if employers
provided them (Salvatore et al., in preparation)
- Workers appreciated warm water, but the distance to the sinks,
the number of workers using each sink, and the piece-rate pay structure
were barriers to handwashing (Salvatore et al., in preparation)
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- Pesticide Exposure Studies
photo by Lora Santiago
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- Toddlers accumulate more pesticides on their clothing than
younger infants
(Bradman, Whitaker et al. 2006).
- Toddlers also have higher urinary metabolite levels than
younger infants
(Bradman, Whitaker et al. 2006).
- Different ambient pesticide measures were not inter-correlated,
suggesting that single measures are insufficient to classify a
household’s pesticide levels
(Bradman, Whitaker et al. 2006).
- Amongst ambient samples, house dust and floor wipes contained
the highest number an levels of pesticides
(Bradman, Whitaker et al. 2006).
- DAP metabolite levels in spot samples are moderately correlated
with those in same-day 24-hour samples.
- However, levels in 24-hour samples collected three days
apart were not correlated with one another.
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- Mechanism Studies
- Certain genetic characteristics make some people more susceptible to
pesticide exposure than others. For example, the human enzyme paraoxonase (PON1)
detoxifies various organophosphate pesticides with different efficiency
depending on single nucleotide polymorphisms (SNPs) at various position on the
PON1 gene. We analyzed blood samples from mothers and children participating in the
CHAMACOS cohort to determine their PON1 genotype and activity.
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- We found that PON1 activity is very low in newborns, suggesting that they are more
susceptible to adverse effects of pesticides than adults.
(Furlong et al. 2006;
Holland et al. 2006).
- PON1 activity was particularly low in newborns with vulnerable PON1 genotype.
Based on their PON1 status, some newborns may be 26 to 50 times more susceptible to
exposure to certain organophosphate pesticides than other newborns. The most susceptible
newborns may be 65 to 130 times more sensitive
to organophosphate pesticides than the least susceptible some adults.
(Furlong et al. 2006
; Holland et al. 2006).
- We treated human blood samples with pesticides, dust mite allergen, and endotoxin,
separately and in combination. We then analayzed 10 different cytokine responses in
the blood using high through-put analysis (Luminex and ELISA). Potentiation of cytokine
response was observed at low doses of the pesticide chlorpyrifos in combination with endotoxin.
(Duramad, Tager et al. 2006).
- We assessed cytokine levels in blood from 24 month children
participating in the CHAMACOS cohort to describe Th1 and Th2 profiles in these children.
Mean Th2 levels were significantly higher in children with asthma diagnosis or symptoms
at age 24 months. Higher concentrations of Th2 cells were associated with maternal work in agriculture
and the presence of a gas stove in the home. Higher concentrations of Th1 cells were
seen in children who weere breastfed and who had pets in the home.
(Duramad, Harley et al. 2006).
- A new radioactive NTE-lysoPLA assay was developed and validated
against the colorimetric lysolecithin NTE assay. The new assay has
improved sensitivity and is suitable for use with small volumes
of biological samples.
- Two new enzymatic activities sensitive to inhibition by
organophosphate pesticides independent of cholinesterase were
found in red blood cells of CHAMACOS pregnant women and newborns.
Characterization in respect to neurotoxicity is in progress
(two papers are in preparation).
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