Forty-four of 182 farmworkers in the study had green tobacco sickness at least once in a 10-week period, said Thomas A. Arcury, Ph.D., of Wake Forest University School of Medicine.
Those 44 workers had 65 occurrences of green tobacco sickness -- including such symptoms as nausea, vomiting, headache and dizziness. "Our study provides the first prospective surveillance data on the prevalence and incidence of green tobacco sickness in any population," said Arcury, associate professor of family and community medicine.
Arcury was a co-author of an article in the American Journal of Industrial Medicine in February 2000 that reported that 41 percent of tobacco farm workers said they had green tobacco sickness at least once in the summer.
The earlier study was based on recall at summer's end. In the new study, the workers were interviewed five times during a 10-week period, and reported sickness as the study progressed, which heightens accuracy.
The research team, which included Sara A. Quandt, Ph.D., professor of public health sciences, John S. Preisser, Ph.D., of the School of Public Health at the University of North Carolina at Chapel Hill and Deborah Norton, M.D., of the N.C. Farmworker Health Program, said, "more effort must be directed toward preventing this occupational illness."
Green tobacco sickness is caused by acute nicotine poisoning resulting from the absorption through the skin of nicotine from the green tobacco plants. The investigators reported that the incidence of green tobacco sickness increased over the course of the growing season, with early-season work, such as topping the tobacco plants to allow the lower leaves to grow more extensively, having a relatively low incidence.
The highest incidence came during harvesting of the tobacco, called priming, when "workers break off ripe leaves and hold them under their arms as they move down the rows until they can hold no more," they said. "As the day progresses, their shirts and skin are stiff with sticky tobacco juice."
They said the axilla, the area under the shoulder joint, absorbs more chemicals than other skin areas, and that is precisely where the farmworkers place the leaves.
In addition, working in wet tobacco or wearing wet clothing is another risk factor for green tobacco sickness reported in earlier studies. The new study found that workers who work in wet clothing for at least 25 percent of the time had twice the incidence of illness of those working in drier clothing.
Arcury and his colleagues said the study probably underestimates the rate of green tobacco illness. The study period ended in early September, but harvesting in that part of the state continues until late September.
The study was conducted at 37 sites in Granville and Wake counties in North Carolina. All but one of the farmworkers had been born in Mexico; the other was a non-Hispanic white man. There were no African-Americans at work at the 37 farms, and only three women.
Some workers at the 37 sites were never enrolled in the study. "For example, at one site visited on a Thursday, the field staff learned that six new workers had joined the crew on Monday (replacing workers who had become sick and left.) These replacement workers had become sick on Monday and moved from the area on Tuesday, giving them no chance to participate in our study," they said. "It does lead us to believe that the actual prevalence and incidence may be higher than we could detect."
Based on study results the researcher team will make recommendations for ways to reduce green tobacco sickness among agricultural workers, Arcury said.