Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study of Latina women and children finds large variation in susceptibility to pesticides

03.03.2006


Some newborns may be 26 to 50 times more susceptible to exposure to certain organophosphate pesticides than other newborns, and 65 to 130 times more sensitive than some adults, according to a new study by researchers from the University of California, Berkeley, and the University of Washington.



The study, to be published Thursday, March 2, in the journal Pharmacogenetics and Genomics, reveals far greater variability in susceptibility to pesticides than previously predicted. Current U.S. Environmental Protection Agency (EPA) standards require an extra tenfold safety factor to protect children compared with adults if there are gaps in information about the children’s susceptibility. The EPA may select a lower safety factor if it determines that enough information is available, and based on an EPA review, many other pesticides have lower or no additional safety factors.

But the new study "raises the question of whether current standards for safe levels of pesticide exposure are sufficiently protective of a vulnerable population," said Nina Holland, UC Berkeley adjunct professor of environmental health sciences and co-lead author of the paper. "Based on our study, I feel that more research is urgently needed to establish whether the standards need to be re-evaluated."


Since 2001, home use of organophosphate pesticides - diazinon and chlorpyrifos, in particular - has been restricted by the EPA, mainly because of risk to children. However, the researchers said there may still be residual exposure to diazinon and chlorpyrifos from household use before they were banned. Some structural uses for the pesticides are still approved, including treatment of house foundations with chlorpyrifos.

While household use of diazinon and chlorpyrifos is now restricted, these and other organophosphate pesticides are still widely used in agriculture. According to state figures, approximately 143,000 pounds of diazinon and 52,000 pounds of chlorpyrifos are used annually in the region studied - California’s Salinas Valley, an agricultural community.

The study, conducted through UC Berkeley’s Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), included 130 Latina women and their newborns living in the valley. The researchers report that approximately 28 percent of the women in the study had worked in the fields during their pregnancies, and another 14 percent had other jobs in agriculture that included nursery or greenhouse work. Overall, 82 percent of the women had agricultural workers living in their homes during their pregnancies.

Various studies are underway to determine the levels of pesticide exposure to residents in both agricultural and urban/suburban communities in California and elsewhere around the country.

The researchers used levels of paraoxonase 1 (PON1) activity measured in blood samples as a marker for pesticide susceptibility. PON1 is an enzyme that breaks down the toxic metabolites of organophosphate pesticides, including diazinon and chlorpyrifos.

"The significance of PON1 has been shown in prior animal studies," said Clement Furlong, research professor in the departments of medicine and genome sciences at the University of Washington, and co-lead author of the paper. "In these studies, exposure to low levels of organophosphates has killed mice that lacked the PON1 enzyme, while the same dose elicited no symptoms in mice with normal levels of the enzyme. Both the quantity and quality of the PON1 enzyme is important in determining the ability to detoxify pesticides."

Furlong pointed out that there is a greater risk when dealing with exposure to the much more toxic, oxidized forms of chlorpyrifos and diazinon, or chlorpyrifos oxon and diazoxon, respectively.

"Chlorpyrifos and diazinon are manufactured as sulfur compounds," said Furlong. "But these pesticides can transform into chlorpyrifos oxon and diazoxon before or after they are applied and then by specific enzymes when they are inside the body. The enzyme we studied breaks down these oxidized forms. Lower enzyme activity means less protection. Risk assessments should consider exposures to these oxidized forms. We also need more field research to quantify the levels of these oxidized compounds in the environment."

The ability of the PON1 enzyme to protect the body from the toxicity of pesticides is determined by genetics, specifically whether a person has the Q or R form of the PON1 gene at position 192 on the chromosome.

People with the QQ genotype have two copies of the Q variant of the PON1 gene, producing a PON1 enzyme that is significantly less efficient at detoxifying chlorpyrifos and chlorpyrifos oxon. People with the RR genotype have two copies of the R variant of the PON1 gene, producing a PON1 enzyme that is more resistant to chlorpyrifos and chlorpyrifos oxon exposure. Inheriting one type of gene from each parent leads to a QR genotype with intermediate sensitivity to chlorpyrifos and chlorpyrifos oxon.

In addition to the factors affecting the type of PON1 enzyme produced, there are additional genetic variants that affect the levels of enzyme available. A recent study of Latino mothers and children from the CHAMACOS group found that several markers of genetic variability have a stronger effect on enzyme activity in children than in adults.

It is mainly the level of PON1 enzyme that determines resistance to diazinon or diazoxon exposure.

The PON1 enzyme also varies by ethnicity. Approximately 10 to 20 percent of African Americans have the QQ genotype, compared with 50 percent of whites. Approximately 25 to 35 percent of the Latino population has the QQ genotype.

For all groups, infants are at particular risk because the level of PON1 enzyme in newborns averages one-third or less than that of adults. It can take six months to two years for a baby to develop mature levels of PON1.

"People have this remarkable difference in enzymes that defend their health from pesticide exposure," said Holland. "In developing regulatory standards for safe levels of exposure, we need to protect the most sensitive in a population, particularly because children and unborn fetuses are involved."

Researchers were able to estimate sensitivity in mothers and children using data on transgenic mice that carried human Q or R genes and that produced levels of PON1 comparable to that in human newborns and some adults. Combined analysis of the animal model data from Furlong’s laboratory and PON1 results from the CHAMACOS cohort allowed a more specific estimation of pesticide sensitivity than was previously possible.

The results of this analysis predict that some newborns may be 26 times more susceptible to diazinon and diazoxon exposure than newborns with the highest PON 1 enzyme levels and up to 65 times more susceptible than adults with the highest enzyme levels.

The differences are even greater when predicting susceptibility to chlorpyrifos and chlorpyrifos oxon. Some of the QQ newborns may be 50 times more susceptible to this pesticide than RR newborns with high PON1 levels, and 130 to 164 times more susceptible than some of the RR adults.

"Several animal studies have shown adverse effects on neurodevelopment from exposure to organophosphates," said Brenda Eskenazi, UC Berkeley professor of epidemiology and director of CHAMACOS and the Center for Children’s Environmental Health Research. "Our next step is to look at the relationship between pesticide exposure and neurodevelopment, specifically for young children and genetically susceptible populations."

Other co-authors of the study include Rebecca Richter, research scientist at the University of Washington; Asa Bradman, associate director of CHAMACOS at UC Berkeley; and Alan Ho, research assistant at UC Berkeley.

Liese Greensfelder | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Studies and Analyses:

nachricht Study relating to materials testing Detecting damages in non-magnetic steel through magnetism
23.07.2018 | Technische Universität Kaiserslautern

nachricht Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>