Photodamage and skin cancer among paraquat workers

Some workers in paraquat manufacturing, exposed to bipyridines, have developed pigmentation and keratosis on sun-exposed skin. This condition has been described as skin-malignancy or premalignancy. This study was designed to clarify the pathologic features of these lesions and to explore the etiologic role played by bipyridine.

Twenty-three biopsy specimens, obtained from the affected skin of 10 workers, were scrutinized by a dermatopathologist. A total of 242 exposed workers from 28 paraquat factories were examined and interviewed during the period from 1983 to 1991. The severity of the characteristic skin lesions was graded from the lowest to the highest response to analyze the data by Mantel extension for a trend that focused on the heavy exposure to bipyridines as risk factor.

All pathology specimens showed various degrees of solar damage: early actinic change, solar lentigo, actinic keratosis (AK), AK coexisting with squamous cell carcinoma (scc), and scc. Six specimens from four workers were scc or scc in situ. Three of six scc showed the coexistence of AK. Of the workers, 133 had skin lesions ranging in severity from grade 1 to grade 3 on sun-exposed areas. The severity of skin changes is strongly associated with heavy exposure to bipyridines (P < 0.0001).

This pathologic study proves that all the lesions showed either photodamage or skin cancer. The strong trend in the correlation between severity of photodamage and exposure to bipyridine leads to the speculation about the synergistic role of bipyridine exposure and the solar effect in causing these malignant and premalignant skin lesions.