Student Research: Ingeborg Cox
, Occupational and Environmental Medicine (OEM), 2009
Faculty Advisor: Matthew C. Keifer
Testing Validity of Audio Computer Assisted Self Interview (ACASI) Among Low Literate Pesticide Handlers
Thousands of migrant workers harvest crops in the State of Washington. Many handle pesticides that can cause harmful effect and even fatalities in humans. A National Institute for Occupational Safety and Health (NIOSH) report identified 3,271 cases of acute occupational pesticide related illness in ten U.S. states, including Washington, in a seven-year span ending in 2005 (Calvert et al., 2008). Of the states evaluated in the study, Washington ranked second highest in the number of poisoning cases (Calvert et al., 2008). In 2007, approximately 589,000 pounds of three common organophosphate and carbamate insecticides with possible neurotoxic effects were applied to apple orchards in Washington State (Hofmann, 2008).
The Washington Industrial Safety and Health Act of 1973 (WISHA) was designed to protect safety and health of employees in the state. As early as 1986, farm workers represented by a legal service agency began a series of four requests to the state’s Department of Labor and Industries (L&I) to require medical monitoring of pesticide handlers. All were denied. As a result, a class action lawsuit was filed in a state court in 1997 (Washington State Labor Council, 2007). The Washington Supreme Court ruled in 2002 that L&I had violated WISHA by denying farm workers’ request for rulemaking on mandatory monitoring (Harrington, 2002). Subsequently, L&I required Cholinesterase (ChE) monitoring for all employees who handle organophosphate (OP) and N-methyl carbamate (CB) pesticides (WA State Register, 2003).
Organophosphate and carbamate pesticides inhibit the activity of the enzyme acetyl cholinesterase (AChE) (WA State Register, 2003). Chemicals that interfere with the action of cholinesterase are potent neurotoxins. Symptoms of mild exposure include headache, anxiety, sleep disturbance, salivation and loss of appetite. Severe poisonings can lead to seizures, and some are associated with delayed neuropathy and paralytic process called intermediate syndrome (Rosenstock, Cullen, Brodick and Redlich, 2005). Also, low levels of organophosphate exposures can lead to long-term neurological impacts (Farm Worker Pesticide Project, 2006). Examples of organophosphate and carbamate pesticides commonly used in Washington State include chlorpyrifos (Lorsban or Dursban), azinphos-methyl (Guthion), carbaryl (Sevin), phosmet (Imidan), diazinon, and malathion (Department of Labor and Industries, 2006).
In 2005, employers were required to refer workers for ChE testing who handle OP and CB pesticides 30 or more hours in any consecutive 30-day period. (The Scientific Advisory Committee, 2006). It was also recommended that workers have a valid baseline blood ChE level drawn (The Scientific Advisory Committee, 2006). A drop in red blood cell cholinesterase (AChE) by 30 percent or more, or in serum cholinesterase (BChE) by 40 percent or more, requires removal of the worker from exposure to pesticides that depress cholinesterase. The worker may go back to handling pesticides when his or her cholinesterase levels return to within 20 percent of baseline (Division of Occupational Safety and Health Directive, 2008).