Environmental Factor, April 2007, National Institute of Environmental Health Sciences
Epidemiology Branch Hosts Annual Advisory Meeting
By Eddy Ball
On February 22 and 23, the NIEHS Epidemiology Branch convened the 14th annual meeting of the Agricultural Health Study(http://www.aghealth.org/) (AHS) National Advisory Panel (NAP) in Rodbell Auditorium. The meeting gave an audience of scientists, educators, concerned citizens and pesticide manufacturers' representatives an opportunity to hear about the progress and future plans of the study.
AHS is a research effort by scientists at NIEHS, the National Cancer Institute (NCI) and the Environmental Protection Agency (EPA) working with collaborators at the University of Iowa and the Battelle Centers for Public Health Research and Evaluation in North Carolina. The National Institute for Occupational Safety and Health and the National Center on Minority Health and Health Disparities also have provided support for the study, and individual studies routinely have included extramural scientists as collaborators or principal investigators.
The goals of AHS are to investigate the effects of environmental, occupational, dietary and genetic factors on the health of the agricultural population. Through more than 82 publications in peer-reviewed journals, AHS has translated its epidemiological findings into information that agricultural workers can use in making decisions about their health and the health of their families.
The study is in the final two years of its third phase of funding. AHS is currently performing Phase III follow-up phone interviews and preparing add-on epidemiological studies of select populations from its more than 89,000 subject cohort in Iowa and North Carolina. Although some in the cohort are now near or in retirement, at the time of their enrollment (1993-1997), subjects were active private and commercial pesticide applicators and the spouses of these applicators.
Fact sheets produced by the study have influenced pesticide certification and educational programs in both Iowa and North Carolina, where applicators have become more sensitive to the importance of protective equipment and proper application practices. Cohort updates provide subjects in the study with summaries of research findings and help to keep retention rates high.
The meeting began with an overview by AHS Project Officer Michael Alavanja, Dr. P.H., of NCI, who underscored the statistical power of the AHS cohort. According to Alavanja, AHS researchers have documented over 900,000 person years of observed health history, including over 5,000 incident cancer cases and more than 5,000 deaths. Response rates to follow-up interviews remain high, due primarily to the careful design and timing of questionnaires.
Following reports on field station activities in North Carolina and Iowa, NCI Staff Scientist Joe Coble, ScD., reported on modifications to the pesticide exposure algorithm, which assigns numerical weights to the various behaviors, such as glove use and application methods, associated with exposure intensity. New pesticides and changes in practices make modifications necessary, Coble explained, but there are also opportunities to incorporate additional factors and molecular data. Panel members discussed whether the project should continue to add variables to the metric - and risk distorting it - or leave it as it is - and possibly miss an important variable.
The remainder of the meeting was devoted to reports by lead researchers on add-on studies evaluating links between pesticide and other farming exposures and prostate cancer, asthma, Parkinson's disease and puberty among the children of cohorts (see sidebar for more detail). Some of these initiatives present researchers with recruitment and informed-consent challenges, as well as the need to incorporate molecular assessments.
As the AHS looks forward to the completion of Phase III in 2008 and beyond, its scientists are asking questions about several key matters, including incorporating studies of additional diseases into the project, the handling of biological specimens, the impact of new practices in pesticide applications, secondary exposures and the growing number of minorities involved in agriculture. AHS wants to expand the translation of its research into public health, consumer protection and occupational safety programs, and policy and to enhance communication with the clinical community.
AHS - Revisiting Past Research Findings and Taking New Directions
During both enrollment and through follow-up interviews every five years, AHS participants provide detailed information about their lives and pesticide use. During Phase II (1999-2003), participants in the AHS provided buccal (inside cheek) cell samples in saliva. Carefully stored since collection, these cell samples will now provide researchers with tissue for DNA analysis. Testing of the original buccal cell samples and, in some cases, newly collected samples is an important component of an ongoing prostate cancer study at NCI.
- Prostate Cancer - Michael Alavanja, Dr. P.H., will explore possible gene-environment interaction in prostate cancer. Alvanja's earlier research with subjects who had developed prostate cancer found an association between pesticide use and cancer, but only among men with a family history. Comparing the genetic polymorphism data from those cancer patients and men who do not have the disease may help researchers pinpoint specific genes that are affected by the environment to trigger prostrate cancer.
- Asthma - Jane Hoppin, ScD., will build upon earlier findings that farmers have a greater risk of developing asthma, but that growing up on a farm offers protection against allergic disease. In a proposed study of 4000 farmers and their wives, Hoppin will conduct pulmonary function testing, collect blood for DNA and other analyses, and collect dust to look at non-pesticide related factors for disease.
- Parkinson's Disease - Freya Kamel, Ph.D., was a lead author on earlier investigations into the association between pesticide use and Parkinson's Disease in the AHS cohort. Kamel and others from the AHS are collaborating with The Parkinson's Institute on the Farming and Movement Evaluation (FAME) Study, a study nested in the AHS cohort, which conducted in-home movement assessments and collected blood and dust to look at potential Parkinson's disease determinants.
- Predictors of Early Puberty - Dale Sandler, Ph.D., will be the lead researcher on the Growth and Puberty Study among Young People in Iowa (GAP). Sandler will study the associations between exposure to hormonally active chemicals by children between the ages of 7 and 15 in farm families and several health conditions related to endocrine disruption. The study will involve recruiting the children of AHS cohort members and utilize non-invasive measures of hormones in saliva and urine.