New Research Findings: Chronic Health Symptoms Caused by Pesticide Exposure, Worse with Greater Exposure

Written by Anthony Hardie, 91outcomes

(Washington, DC - November 2, 2009) - Neurological symptoms are caused by exposure to pesticides and are made worse with certain kinds of pesticide exposure and duration of exposure, according to scientific research presented today in Washington, DC by Dr. Freya Kamel, staff scientist with the Chronic Disease Epidemiology Group of the National Institute of Environmental Health Sciences (NIEHS).

In the presentation before the Congressionally chartered Research Advisory Committee on Gulf War Veterans' Illnesses (RAC), entitled, "Chronic health effects from pesticides: results from the Agricultural Health Study," Dr. Kamel noted that scientific findings found early evidence of neurological dysfunction related to pesticide exposure--especially organophosphates--before the appearance of apparent clinical signs normally identified during a physician's neurological examinations.

Exposures during the 1991 Gulf War to high levels of highly concentrated forms of two organophosphate pesticides, DEET and permethrin, in conjunction with exposure to Pyridostigmine Bromide (PB), a nerve agent protective pill, were identified as causes of Gulf War Illness in a 2008 U.S. Government scientific report showing that Gulf War Illness is real.

Groups of neurological symptoms identified in Dr. Kamel's team's research included affect, cognition, autonomic and motor function, and vision.

Affect:

* Anxiety (52%)
* Irritability (37%)
* Depression (27%)


Cognition:

* Memory (24%)
* Concentration (20%)


Sensory:

* Numbness or paresthesia (27%)
* Poor night vision (12%)
* Blurred or double vision (10%)
* Changes in taste or smell (6%)


Motor:

* Twitches (17%)
* Weakness (15%)
* Poor Balance (12%)
* Tremor (11%)
* Difficulty Speaking (4%)


Autonomic:

* Nausea (27%)
* Loss of appetite (18%)
* Excessive sweating (17%)
* Fast heart rate (15%)


Other:

* Headache (68%)
* Fatigue (58)
* Insomnia (43%)
* Dizziness (28%)
* Loss of consciousness (2%)


According to Dr. Kamel, acute, high level pesticide poisoning has long been recognized as having severe acute symptoms and likely long-term issues resulting from those exposures. However, this study was a cross-sectional study that began with 90,000 pesticide workers and their families and looked at chronic effects of long-term, lower-dose exposures to pesticides and had profound results.

The study, based on Phase I data, was restricted to applicators who completed a take-home questionnaire and collected symptom and exposure data at the same time, a potential study weakness. However, the study also examined participants' exposure levels and to different types of varied widely, identified by Dr. Kamel as, "an advantage, because we were comparing those with high level exposures to those with low level exposures."

The results suggested that neurologic symptoms are associated with cumulative exposures--exposures over time that have added up--to moderate levels of organophosphate and organochlorine insecticides and suggested permanent residual damage caused by these exposures. The cumulate lifetime use of insecticides is associated with increased risk of having greater than 10 of the measured symptoms in the prior year.

With regards to functional pesticide groups, negative health outcomes were linked primarily to insecticide and herbicide agents, and less so to fungicides and fumigants. However, there was a strong association with fungicides and age-related macular degeneration (AMD), a leading cause of progressive blindness.

With regards to insecticide chemical groups, organophosphates were heavily linked to negative health outcomes, while organochlorines and carbamates were associated with negative health outcomes in about half the cases. Pyrethroids, the last of the four insecticide chemical groups, was associated with negative health outcomes in about one-fifth to one-fourth of the cases.

DEET and permethrin, two pesticides used commonly at high concentrations by 1991 Gulf War troops, are organophosphates, as is Agent Orange, an herbicide used widely during the Vietnam War and linked to a host of serious, negative health outcomes among veterans of the Vietnam War and the indigenous Vietnamese population.

Parkinson's Disease, a neurodegenerative disease with early symptoms that include tremor, slow movement, and postural instability, along with soft voice and small handwriting, was also associated with pesticide exposures.

Dr. Kamel's research focuses on environmental determinants of neurologic dysfunction and disease, in particular, neurodegenerative disease.

Kamel received a B.A. in mathematics from Brandeis University and a Ph.D. in biological sciences from SUNY-Binghamton. She did research in neuroendocrinology as a postdoctoral fellow at The Rockefeller University and then as an assistant professor at The Rockefeller University and the University of Wisconsin. She received an M.P.H. in epidemiology from the University of North Carolina at Chapel Hill. She joined the Epidemiology Branch at NIEHS in 1989, and currently serves as an epidemiologic consultant for the National Toxicology Program, an associate editor of the American Journal of Epidemiology, and a member of the editorial board of Environmental Health Perspectives.