 This study suggests that dogs can be used as sentinels for human exposure to certain chemicals. Urinary levels of acrolean, arsenic, and forchlorophenol were found to be significantly higher in dogs than in humans, suggesting that these chemicals are present in the environment and could be contributing to increased risk of cancer in humans. This article was authored by Kate Lynn Cron, Christopher Ross Lutocque, Martin Schaefer, and others.