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AgHealthNews

Issue Number 2001-04
Fall 2001

2001-04-01 Table of Contents

2001-04-02 Welcome and Introduction

2001-04-03 Researchers Conduct PM-10 Study in California's Central Valley

2001-04-04 Spanish Physician Compares Results of Respiratory Studies

2001-04-05 Organophosphates--Toxicologist Describes Medical Challenges of Health Care Providers in South Asia

2001-04-06 Studying Pesticide Exposure in Costa Rica

2001-04-07 Center Investigator Earns Fulbright

AgHealthNews is an electronic version of the Center's quarterly newsletter. The Center has two electronic list servers that allow automatic forwarding of e-mail to a list of subscribers. One server is a forum for announcements and discussion of agricultural health and safety issues and the other is a vehicle for the automatic distribution of the Center's quarterly newsletter.

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Many ongoing studies are intended to determine the risk for particle exposure. Increased knowledge about the composition of dust in certain areas is necessary to help reduce harmful effects of dust exposure on the population working and living in those areas.

Two researchers in the UC Davis Department of Land, Air and Water Resources, who have been evaluating "fugitive" dust in California's San Joaquin Valley, were guest speakers on Sept. 14 at the Center's first noon seminar of the 2001-2002 academic year. Postdoctoral scholar Mara J. Johnson, Ph.D., and graduate research associate Rebecca Domingo Neumann, M.S., presented "Mineralogical and Microbial Characterization of Dust from the Central Valley of California" in the new seminar location, the Foster Room in Meyer Hall.

Neumann and Johnson have been investigating PM-10--particulate matter measuring 10 microns or less--in the San Joaquin Valley, which has been cited for its substandard air quality. Neumann explained that 30 to 60 percent of the PM-10 is actually derived from soils. "We're concerned about the health aspects of PM-10, especially in the agricultural area where the farm is not only a place of work but could also be a place of residence. Groups at higher risk include those with asthma and cardiovascular disease," she said.

Neumann's work involves identification of the mineral composition characterizing PM-10. During her research, Neumann collected samples from upwind and downwind directions at distances of 10, 50, 100, 150 and 200 meters from the area of an agricultural operation in the Central Valley. Using analytical methods, including Proton-Induced X-Ray Emission (PIXE), Electron Probe Microanalysis (EPMA), Scanning Electron Microscope and X-Ray Diffractiometry, Neumann identified materials derived from different rock sources on the west side (Lost Hills)--primarily sedimentary and metamorphic rocks-and the east Side (Shafter)--igneous rocks--of the Central Valley. "From these rock materials, we have soil-forming minerals," she said. "The biolite-like materials contain titanium, which we found more prevalent on the east side. Iron was also higher on the east side."

Johnson is applying molecular biology techniques to soil science in evaluating whether microbial populations and the potential source of fugitive dust could distinguish its source. "By `fugitive,' I mean dust floating around and trapped in the lower portion of the Central Valley. It's gotten away from its source and is contributing to the PM-10 problem," says Johnson.

Both investigators agree that the potential sources of poor air quality in the Central Valley include material stirred up by tires on paved and unpaved roads, agricultural tillage practices, and construction operations. Johnson's agricultural samples were derived from cotton, almond, grape, tomato and safflower farming. She also included samples from a cattle feedlot and dairy, roadway samples, and some exposed soil samples. Johnson compared the soil microbial DNA fingerprinting to those DNA fingerprints from dust generated from the soil.

"We created a sample dust generation chamber, and used a sophisticated image analysis software program called GEL Compare, specifically tailored for DNA fingerprinting," she said.

Detection methods that were developed during this study prove promising for issues of grave public concern. "For example, this detection method could potentially detect bio-warfare agents. Anytime you capture microbes on a filter, this technique can be used," said Johnson. "This method might also be used to track pathogens to their origin, for example, in the case of Valley Fever in the Central Valley. It has potential for many occupational health studies."

A chest physician at the Hospital Germans Trias i Pujol and researcher at Fondo de Investigaciones Sanitarias de la Seguridad Social in Badalona, Catalonia, Spain, Eduard Monso, M.D., was invited to spend three weeks at UC Davis in July comparing results. The European study, involving Monsó and numerous other investigators from Denmark, Germany, Switzerland and Spain, was published in a report titled "Respiratory Symptoms of Obstructive Lung Disease in European Crop Farmers." The report appeared in Vol. 162 of the American Journal of Respiratory Critical Care Medicine, pp. 1246-1250, 2000.

Conducted between 1995 and 1997, the study is a cross-sectional examination of 4,793 crop farmers from the four European countries. The study was intended to determine the prevalence of respiratory symptoms of obstructive lung disease in farmers producing different crops and to assess the role of specific crops as risk factors. European investigators also set out to determine whether work inside greenhouses might be related to an increase in the prevalence of respiratory symptoms.

"The work Dr. Marc Schenker is doing in California has similarities to a study I'm performing involving European crop farmers," said Monso. "I'm from Barcelona, Spain, which has some similarities with your climate, and both places have quite diverse types of crop farming."

Although farms in the European countries studied tended to be smaller than farms in the United States, both studies included hired farm laborers; however, in Europe farm employees were primarily from the local population versus the transient workforce characteristic of California farms.

During his visit, Dr. Monso found a significant difference in respiratory symptoms in U.S. farmers. Data from the California study revealed a greater prevalence of high fever and asthma, whereas the data from the European farmers indicated a higher prevalence of chronic bronchitis.

Dr. Monso acknowledged the fact that European farmers may include more smokers than California farm workers, but says chronic bronchitis symptoms were also found in nonsmokers. "It could be due to more work in enclosed buildings with farm animals," he says, "or perhaps because the European farmers spend more hours per week in enclosed buildings."

The European study showed no significant difference in the prevalence of respiratory symptoms between farmers cultivating vegetables/tomatoes and those growing fruits and nuts. However, it revealed that cultivation of flowers or oil plants was associated with two or more respiratory symptoms. Flower farmers had significantly higher prevalence of wheezing (20.1%), asthma (5.4%), chronic phlegm (16.1%), and organic dust toxic syndrome (19.4%), when compared to farmers or vegetable crops. Organic dust toxic syndrome (ODTS) was also observed in workers cultivating oil plants (18.3%), grain (16.1%), and root crops (17.8%).

"Because results of the comparison study were quite interesting, we plan to prepare a paper to be published in an international journal," said Monso.

For more information on the European study or Dr. Monso's comparison study, he can be reached by e-mail at emonso@ns.hugtip.scs.es. Abstracts from the Center's respiratory studies may be found at http://agcenter.ucdavis.edu/ under "Current Research Projects."

Conceived as insecticides, these compounds also have been developed to become the most feared of chemical weapons. The control of vectors of diseases from which millions of people die or are disabled is heavily dependent upon organophosphates, as are the efforts to maintain food production in the face of uncontrolled population growth, diminishing arable land and the possibility of global warming. As the toxicity of organophosphates is non-specific, it has caused ill health and death in humans and has contributed to adverse ecological effects.

Toxicologist Lakshman Karalliedde, MBBS, DA, FRCA, of the Medical Toxicology Unit and Poisons Information Service at Guy's and St. Thomas' Hospital Trust in London, presented a talk titled "Organophosphate Poisoning in South Asia: variables influencing the human response to organophosphates and the intermediate syndrome" at UC Davis on June 15 in the Foster Room of Meyer Hall.

Born and educated in Sri Lanka, a south Asian island in the Indian Ocean, Karalliedde was a consultant anaesthetist with a major interest in poisoning, particularly organophosphate poisoning, for more than 25 years. During his work in Sri Lanka, Karalliedde treated people with diseases and life-threatening conditions, including tetanus, rabies and snake bites, with limited facilities and technology.

"Following postgraduate training in the UK, I came under the influence of Stanley Feldman in Sri Lanka, and I had the good fortune of working with academics like professors Nimal Senanayake and Arjuna Aluwihare. We had patients in vast numbers, and we had to treat them the best we could," said Karalliedde.

Some of the obstacles that Karalliedde and his colleagues faced included:

Karalliedde and his family moved in 1989 from Sri Lanka to the United Kingdom, where he began his career as consultant anaesthetist at the Ministry of Defense while also conducting research and serving as senior lecturer at National Poison Center at Guy's and St. Thomas' Hospital Trust in London. After joining the Medical Toxicology Unit of Guy's in 1998, Karalliedde became actively involved in research involving organo-phosphates and their affects on human health.

Karalliedde's new book, Organophosphates and Health (ISBN 1-86094-270-9) primarily covers health aspects related to exposure to organophosphates with discussions on related social, economic, environmental and agricultural issues. The book presents information in a manner that basic scientists, medical personnel, environmentalists, agriculturalists and those in public health and occupational medicine will find essential when considering the use of organophosphates in their disciplines. Published by Imperial College Press (www.icpress.co.uk) and co-written with S. Feldman and John A. Henry from Imperial College, U.K.; and T. Marrs of the Food Standards Agency, U.K.; Organophosphates and Health was released in July.

More than 300 workers from coffee, banana and palm oil farms throughout Costa Rica are being recruited for the study. The workers will complete a work history questionnaire and undergo pulmonary function and exercise testing.

Paraquat is used in more than 130 countries for weed control. Valued for its effectiveness, rapid decomposition in soil and lack of a toxic residue, it is commonly used in California. It is also heavily used in Latin America, where the tropical climate intensifies the need for a quick-acting herbicide. In the United States, only certified applicators are permitted to use Paraquat. Several countries, including Finland, Sweden and Austria, ban its use completely. In Costa Rica, however, no restrictions exist, and people can purchase Paraquat for their own gardens.

Case reports of accidental poisonings and suicide attempts have shown that, at high doses and without immediate medical treatment, Paraquat causes severe lung damage and respiratory failure; however, the health effects of chronic low-level exposure are not well understood.

Center Director Marc Schenker, and Kiyoung Lee, an exposure assessment specialist, are addressing this question with Laurel Beckett, professor of epidemiology and preventive medicine, and Bruce Hammock, professor of entomology in the UC Davis College of Agriculture.

"This study is one of the largest and most intensive to be conducted in this population," said Schenker, a physician known internationally for his work on improving the working conditions of agricultural laborers. "We hope these studies provide a more definitive answer to the question about the safety of chronic low-level Paraquat exposure."

For more details about the study, visit http://www-epm.ucdavis.edu/www/Projects/salud/Intro.htm.

Reprinted with permission of COEH, University of California. This article first appeared in the June 2001 issue of COEH Bridges.

Boucher is one of approximately 2,000 American grantees who traveled abroad for the 2000-2001 academic year through the Fulbright program.

Established in 1946 under legislation introduced by the late Sen. William J. Fulbright, the program is designed to build mutual understanding between the people of the United States and the rest of the world.

Boucher taught classes in occupational health research to students and health care professionals in Thailand during her four-month fellowship.

As co-investigator of a Center-funded research project for the UC Agricultural Health & Safety Center at Davis, Boucher trained volunteers to educate Hispanic women farm workers about the importance of Pap smears.

The incidence of cervical cancer and death from cervical cancer is higher in Hispanic women than any other group in the United States. Pap smears detect cervical abnormalities long before they become malignant and help make cervical cancer a virtually preventable disease.

Recipients of Fulbright awards are selected on the basis of academic or professional achievement and leadership abilities. Since 1946, some 86,000 Americans have studied, taught or performed research abroad.

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