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Epidemiology and Preventive Medicine
Biomarkers of Pesticide Exposure
Developing, Improving and Applying Cost-Effective and
Accurate Human Blood Cholinesterase Determinations Research B (Barry Wilson). Blood
cholinesterases are important enzymes for monitoring exposures
to agricultural chemicals and nerve agents of warfare and terror.
We showed that commonly used kits for measuring cholinesterases
are not optimal for determining acetylcholinesterase (AChE) activity
yielding results that are not reproducible between clinical laboratories.
Such findings led to a revision of the California regulations
requiring clinical laboratories to standardize their results.
Laboratories
were contacted and invited to participate in a split sample study
of human blood AChE and non-specific cholinesterase (BChE) assays.
Laboratories measured erythrocyte (RBC) AChE and/or plasma BchE
activities from undiluted and 50% diluted blood according to
their practices. Aliquots were sent to Wilson's laboratory
at UC Davis
for assay using an optimized semi-automated plate reader version
of the method of Ellman. Nine of 25 laboratories participated;
two did their own comparisons. Best correlations were obtained
with BChE activity. Acceptable correlations were 0.88 or above
for 4 of 5 laboratories for BChE and 0.9 or above for only 2
of 7 laboratories for AChE. A bovine AChE RBC ghost "standard" was
devised, tested and validated. The overall poor correlation of
inter-laboratory cholinesterase results indicates an urgent need
to standardize clinical procedures. Work continues with the clinical
laboratories, first with comparing RBC ghost values and then
with samples of whole blood. Supported by UC Davis NIOSH Center
for
Agricultural Health and Safety CDC U07/CCU906162-06), NIEHS Center
for Environmental Health Science (ES05707), CA Offices of Environmental
Health Hazard Assessment (99-E0021) and Department of Pesticide
Regulation (98-0321).
Best Management Practices for Pesticide Use and Food
Safety Among California's Small Farmers with Particular Reference
to Limited
English Speaking & Cultural Minority Farmers (Education B) (Desmond
Jolly). The project aims to maximize the impact of educational
interventions with respect to the adoption of ‘best practices’ in
pesticide use as well as in the management of microbiological
hazards in agricultural production, post-harvest and marketing.
By implication,
if these intervention methods are effective, we will reduce the
incidence of injuries and illnesses associated with these risk
factors.
Various communication tools and media will be utilized in channeling
the information to growers. A longitudinal study utilizing random
surveys each year for the next five years will track changes
in levels of awareness, knowledge, motivation and adoption of
acceptable ‘best
practices.’ Surveys and focus groups will also be used to evaluate
the role and importance of alternate channels of communication.
We will test whether communication channels and tools vary in
terms of their effectiveness across different socioeconomic and
demographic
groups. This will inform our knowledge base as to how to more
effectively transmit information to affect the behavior of a
multicultural
farm population.
Development and Implementation of Pyrethroid and Paraquat
Immunoassays for Human Exposure Monitoring (Pilot 2) (Bruce Hammock). One goal
of this project is to develop, validate and implement rapid immunochemical-based
analytical methods to monitor human exposure to pesticides in farmworkers.
Our focus pesticides are paraquat and pyrethroids. There are more
than 20 pyrethroids frequently used in agriculture, most of them
contain a phenoxybenzyl group in their structures. Although selective
metabolite assays for each pyrethroid are important when exposures
are known, a class specific assay to metabolite m-phenoxybenzoic
acid (PBA) is very useful and efficient for epidemiology studies
and human exposure monitoring. Thus, validation of an immunoassay
for PBA in human urine is included in this project. Paraquat, a
heavily used herbicide, is a toxicologically and epidemiologically
important compound. A more sensitive and selective assay is needed
for human exposure monitoring. Finally, we will explore a new detection
system using novel fluorogenic enzyme substrates toward increasing
sensitivity and sample throughput.
The project has three specific aims. First, validate class-specific
and compound specific pyrethroid immunoassays for human urinary
monitoring; optimize immunoassays for the pyrethroid metabolite
m-phenoxybenzoic acid; and validate the optimized assays in human
urine samples. Second, develop a compound-specific immunoassay
for paraquat; design and synthesize haptens; generate antibodies
and screen haptens; and optimize assays and validate them in human
urine. Finally, develop and apply fluorogenic alkaline phosphatase
(AP) assays for ELISA; design and synthesize novel alkaline phosphatase
(AP) specific substrates; screen AP substrates with model enzymes;
optimize and evaluate the selected AP substrates for application
to enzyme immunoassays; and investigate fluorogenic AP substrate
assisted immunoassays for human exposure monitoring to pyrethroids
and paraquat.
Epidemiology of Agricultural Injury and Ergonomics
Safety Education and Agricultural Injury among Rural
California High School Students (Research F) (Stephen McCurdy). In spite of
its status as one of the nation's most hazardous industries, agriculture
is unique in utilizing significantly more child labor than other
less hazardous industries. Approximately 1.3 million persons younger
than 20 years of age live on U.S. farms according to the 1991 census,
and more than 120,000 children aged 14 perform agricultural work.
There are approximately 100 fatal and 32,000 nonfatal injuries
(15,000 of which are work-related) annually among children on U.S.
farms. Efforts to reduce the toll of agricultural injury have included
engineering improvements, education, and enforcement of existing
laws. Although significant resources are devoted to education,
few data exist to document its impact.
This project is a longitudinal observational study of California
Central Valley high school students enrolled in a state-approved
agricultural curriculum to evaluate the impact of agricultural
safety curriculum on reducing risk and instilling safety attitudes
and behaviors. Approximately 600 students will be followed through
their school years; approximately half will receive the safety
component (taught in Agricultural Mechanics classes) in the state-approved
agriculture curriculum. The remaining students, although enrolled
in the state-approved agricultural program, will not receive the
safety component of the curriculum. Subjects will be surveyed regarding
demographic characteristics, health and health behaviors, agricultural
safety-related attitudes and practices, and injury experience in
the preceding year. The survey will be repeated in subsequent years
for four cycles of data collection. The study will evaluate whether
students receiving the safety component manifest a reduced injury
rate and higher levels of safety-related attitudes and reported
practices compared to their peers who have not received the safety
component of the curriculum.
An Intensive, Regional Approach to Occupational Research
Priorities for California Farm Workers (Pilot 1) (Rick Mines
and David Lighthall). The goal of the proposed pilot research is to conduct a set of
regional, intensive case study investigations of occupational safety
and health problems facing California hired farm workers. The empirical
foundation for the regional case studies is two extensive health
surveys of 1,435 current and former California farm workers conducted
by the California Institute for Rural Studies (CIRS) in 1999. The
California Agricultural Workers Survey (CAWHS) interviewed 968
current farm workers regarding a comprehensive range of occupational
health issues as well as physical examinations and blood chemistry
analyses. Interviews were conducted in seven communities representing
the six agricultural regions of the state. The Binational Health
Survey (BHS) posed a similar range of questions to 162 current
farm workers and 305 former farm workers residing in villages in
Mexico but did not include physical exams. Phase I of the project
consists of a regional assessment of key occupational risk exposure
and related trauma. The regional analysis will particularly focus
on (1) correlations between crop/tasks and chronic trauma and (2)
an evaluation of the effectiveness of Worker Protection Standards
(WPS) in respect to training and minimizing pesticide exposure.
This analysis will serve as the basis for causal hypotheses that
will guide the intensive fieldwork of Phase II. The goal of Phase
II is to systematically investigate the validity of these hypotheses
in their regional contexts via semi-structured interviews with
workers, employers, occupational health specialists, health providers,
and others. Analytical objectives to be included in the final report
include (1) process understanding regarding onset, treatment, duration,
and length of tenure impacts for common chronic injuries in each
region, (2) worker-, care provider-, or employer-based barriers
to treatment for occupational trauma, (3) explanations for WPS
inadequacies in respect to training and compliance, (4) suggestions
for improving access to occupational safety training and health
care, (5) identification of gaps in the regulatory safety net for
hired farm workers in the state, and (6) specification of emergent
research hypotheses that merit follow-up research by specialists
at the Western Center for Agricultural Health and Safety and elsewhere.
Current Costs of Occupational Injuries in Agriculture
(Research E) (J. Paul Leigh). Costs have become critical statistics in the
ongoing debate about medical care. Recently, some estimates have
been made of medical care and productivity costs associated with
job-related injuries across all industries. A recent preliminary
study suggests the industry of agriculture contributes a disproportionately
high cost to the total cost for all industries. But this preliminary
study applies to 1992. We propose to estimate the current (2001-2003)
costs using methods that improve on those of the preliminary study
and conduct a sensitivity analysis that allows for alternative
assumptions.
Fatal injuries will be estimated with data from the Bureau
of Labor Statistics’ (BLS’s) Census of Fatal Occupational Injuries
adjusted for underreporting of minorities. Non-fatal injuries will
be estimated with data from the BLS’s Annual Survey and the National
Institute for Occupational Safety and Health’s Traumatic Injury
Surveillance of Farms (TISF) . The human capital/cost-of-illness
method will be used. Costs will be split into direct and indirect
categories. Within the direct category, we will include medical
care costs, as well as medical and insurance administration. Within
the indirect category we will include lost wages, lost fringe benefits,
lost home production, and hiring and training costs for firms.
Medical costs will be estimated with information from the National
Council on Compensation Insurance (NCCI) as well as the Workers’ Compensation
Insurance Rating Bureau (WCIRB) of California. Administration
costs will be based upon estimated ratios of overhead to benefits
paid
from private and government insurers. Lost wages will be estimated
with a present value function that allows for varying wages and
varying survival probabilities by gender and age. Fringe benefits
and home production will be estimated with published ratios of
fringe benefits to wages within agriculture and published ratios
of home production to wages for those who work outside the home.
Hiring and training costs will be similarly accounted for. These
estimates will apply to each year 2001, 2002 and 2003. We will
also attempt a comparison of agriculture to the costs in all
other industries for the same years.
Prevention of Musculoskeletal Disorders in Hand Harvest
of Vegetable Crops (Prevention B) (John Miles). This
project relates directly to three high priority objectives
in the Healthy People 2000 report:
research on hazard surveillance, development of control approaches,
and effective use of controls. In addition to meeting high priority
objectives in Healthy People 2000 this proposed project also
meets two specific priorities of the National Occupational
Research Agenda.
Specifically, work-related musculoskeletal disorders and special
populations at risk (i.e., nearly all workers involved are immigrants
from Mexico or other Central American countries. The project’s
four main goals are: to improve prevention of high risk musculoskeletal
disorders due to hand harvesting of vegetables; to demonstrate
the application of ergonomic engineering intervention in a field
agricultural workplace; to increase the understanding of the risk
factors for musculoskeletal disorders and ergonomic methods among
owner/operators, workers, and the agricultural community in general;
and to add to research knowledge about ergonomic engineering approaches
to agricultural injury control. The project’s specific aims include:
1) recruit cooperating partners from among vegetable producers;
2) develop detailed ergonomic descriptions (including instrumented
biomechanical, metabolic, and postural data) of identified risk
factors for MSDs involved in hand harvest of leafy vegetables;
3) assess the incidence of MSDs and related symptoms among workers
performing hand harvest of leafy vegetables; 4) study a field-ready
prototype of existing model leafy vegetable harvest machine; 5)
conduct cooperative field trials of prototype with producers; 6)
estimate the impact of the prototype interventions on the ergonomics
of hand harvest work tasks; 7) estimate the impact of the prototype
interventions on the health outcomes; 8) assess productivity impacts
and perceived “adoptability” of interventions; 9) evaluate cooperative
intervention trials and compare with pre-intervention analyses;
10) communicate project findings to vegetable and other agricultural
industry groups, to workers, and to community interests; and
11) report project findings in appropriate research and professional
publications.
Incident Disease and Injury Among a Cohort of California
Farmers and Farm Operators (Research A) (Marc Schenker). Increased morbidity
and mortality from all causes has been well documented in many
agricultural settings, but there have been relatively few studies
of morbidity and mortality among California farmers and farmworkers.
California is the largest agricultural state with production of
$28+ billion in farm commodities annually produced on 81,000 farms
by up to 1.5 million people. This project involves an ongoing series
of health studies among a cohort of California farmers aimed at
identifying the prevalence and risk factors for acute and chronic
disease, and ultimately at the prevention of disease in this population.
The major focus is on hazards predominantly occurring among California
and other Western farmers. The follow-up component allows us to
measure disease incidence and its risk factors and to determine
changes in work practices as this cohort ages. This cohort is closely
connected to the exposure assessment studies of the Center. We
hypothesize that agricultural work increases the risk of acute
and chronic injury and illness, and that these occupational diseases
result in increased disability and mortality.
The cohort was initially contacted in 1993, consisting of a
representative statewide sample of 1,947 California farm operators.
In 1995-96,
we selected a stratified sub-sample of farmers to further investigate
respiratory disease and symptoms. In 1998 we located 1,652
of the participants for a questionnaire follow-up that addressed
incident
disease, and several new outcomes including musculo-skeletal
symptoms and disease. In addition we obtained baseline health
and work information
on 802 spouses (81% response) and enumeration of 600 children
<18 years of age living on the farms of the study subjects.
In years 1 and 2 we will identify a subset of up to 100 farmers
with and without respiratory symptoms from the 1995 case-base sample
and conduct an intensive investigation of respiratory function
and structure, focusing on the effects of agricultural dust exposure.
This will involve extensive pulmonary function testing and HRCT
scanning to characterize pulmonary fibrosis and obstructive changes.
In year 3 we will conduct a follow-up survey of disease and symptom
incidence and prevalence among the full sample of California farmers
whom we surveyed in 1993 and spouses identified in 1998. We will
also request death certificates and analyze cause-specific mortality
for those individuals in the cohort who have died. In year 4 we
will conduct additional case-based analyses of the cohort to identify
specific risk factors for disease in the population. We specifically
expect to study causes of musculo-skeletal symptoms or disease,
although the final case definition will depend on findings of the
cohort follow-up conducted in year 3. The existence of this representative
sample of California farmers and farm managers provides a powerful
tool for hypothesis generation and testing, focusing on agricultural
risk factors for disease in California farmers.
Epidemiology of Agricultural Safety
Extending Pesticide Related Health and Safety Programs
to Underserved Ag Populations in the Western United States (Education
A) (Patrick
J. O'Connor-Marer). This project involves research to
determine the most effective outreach and educational methods
to communicate
agricultural risks to underserved agricultural populations working
in the Western United States. As part of the project, investigators
will research and test established and new methods of extending
agricultural health and safety information to individuals in
these communities. This project’s unique approach involves three areas
of significance: (1) developing and testing effective pesticide-related
health and safety training methods and materials that can be extended
to underserved populations through members of their communities—these
methods and materials will be designed to address the cultural,
language, and educational variabilities of underserved populations
in agricultural communities; (2) devising and testing innovative
and practical techniques to assist agricultural employers of
underserved populations in providing effective pesticide safety
training and
hazard awareness programs; and (3) evaluating effectiveness of
various methods for extending agricultural pesticide-related
health and safety information, resources, and training to health
care
providers, social service organizations, and other leaders within
underserved agricultural communities.
The purpose of these activities is to reduce pesticide-related
illnesses and injuries within the underserved populations and to
develop educational and outreach models that will form the framework
for ongoing, community-based programs for transferring important
agricultural health and safety information and hazard awareness
training to immigrant and Native American farming families and
communities in California, Arizona, Hawaii, and other Western states.
Other Epidemiology A Cross-sectional Study of Respiratory
Function and Paraquat Exposure Among Agricultural Workers in
Costa Rica
(Marc Schenker and Kiyoung Lee). This is a cross-sectional study
of respiratory function and paraquat exposure among agricultural
workers in Costa Rica. The study includes two components: (1) an
exposure assessment component, and (2) an epidemiological study
with interviewer administered questionnaires and pulmonary function
testing, including single breath diffusion capacity and oxygen
desaturation testing. Kiyoung Lee is in charge of exposure assessment.
The specific aims of the exposure assessment are to measure current
paraquat exposure by biological markers in a subset of current
farm workers and to characterize current and cumulative paraquat
exposure among farm workers, based on work histories and exposure
assessment results. This study will evaluate possible independent
association of cumulative long-term paraquat exposure with respiratory
symptoms and pulmonary function in study subjects. In the past
year data collection in Costa Rica was completed. Questionnaire
and pulmonary function data were obtained on 340 agricultural workers
in Costa Rica. In addition, an extensive exposure assessment component
under the direction of Dr. Kiyoung Lee collected air and biologic
samples to assess paraquat exposure in the cohort. Bioassays were
completed at UC Davis under the direction of Dr. Bruce Hammock.
Biological Monitoring of Occupational Exposure to Paraquat
in Costa Rica (Kiyoung Lee). The aim of this project is to measure
paraquat urine level among herbicide applicators and farm workers.
The 24-hour urine samples were collected during application day
and analyzed by ELISA method. This study will provide the exposure
distribution and determinant factor of the occupational exposure
for cross-sectional epidemiological study.
Development of Ultimate Passive Sampler without Face
Velocity Influence on Sampling Rate (Kiyoung Lee). The aims of this research
are to identify mass transfer characteristics of passive samplers
that depend on face velocity, develop a personal sampler configuration
that has negligible face velocity effect on sampling rate, and
evaluate its performance under various conditions. This research
will provide passive sampler configurations that can provide accurate
measurements under fluctuating environmental conditions. Passive
sampler will be an irreplaceable sampling device for exposure assessment,
as long as the face velocity effect during the sampling can be
minimized.
Exposure Assessment of Wood Smoke in Developing Countries
(Kiyoung Lee). The aim of this research is to understand the exposure profile
of wood smoke in developing countries. As a majority of the world's
population is exposed to wood smoke, better understanding of exposure
and its health effects are needed. We measured exposure profile
in Costa Rica, and will measure the exposure in Pakistan. This
information will be critical to understand the reproductive health
effect of wood smoke.
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