Workers who apply certain pesticides to farm fields are twice as likely to contract melanoma, a deadly form of skin cancer, according to a new scientific study.

The researchers identified six pesticides that, with repeated exposure, doubled the risk of skin cancer among farmers and other workers who applied them to crops.

The findings add to evidence suggesting that frequent use of pesticides could raise the risk of melanoma. Rates of the disease have tripled in the United States in the last 30 years, with sun exposure identified as the major cause.

Four of the chemicals – maneb, mancozeb, methyl-parathion and carbaryl – are used in the United States on a variety of crops, including nuts, vegetables and fruits. Two others, benomyl and ethyl-parathion, were voluntarily cancelled by their manufacturers in 2008.

“Most previous melanoma literature has focused on host factors and sun exposure. Our research shows an association between several pesticides and melanoma, providing support for the hypothesis that agricultural chemicals may be another important source of melanoma risk,” according to the report by epidemiologists from University of Iowa, the National Institute of Environmental Health Sciences and National Cancer Institute.

The findings also may have implications for consumers who use pesticides in their homes or yards. Carbaryl, one of the pesticides linked to skin cancer, is the active ingredient in the insecticide Sevin, which is widely used by consumers to kill pests in gardens and lawns.

The study, published last month in the journal Environmental Health Perspectives, examined cancer rates in 56,285 pesticide applicators in Iowa and North Carolina as part of the federal government’s Agricultural Health Study, a large, long-term study of pesticide applicators and their spouses.