Nail injury and diquat exposure: forgotten but not gone.

Primary fingernail changes that result from chemical exposures are seldom encountered in clinical practice. A cluster investigation was conducted on employees at a pesticide packaging company. Six employees reported simultaneous onset of defects occurring in their fingernails, including nail discoloration, nail dimpling, and nail shedding. Multiple pesticides and herbicides including diquat were used in the facility at the time of the cluster onset. A literature review noted 6 articles published before 1975 documenting similar nail changes associated with paraquat, diquat, or other herbicide use. Only one such case report published after 1985 could be located. Diquat was the only material that was previously reported in the medical literature as causing nail defects and also in use at this facility. Diquat exposure is the most plausible explanation for the observed changes in these workers' fingernails.