� Greater than 40% of all households in the U.S. have one or more cats or dogs and many of these animals eat human foods and sleep in bed with their owners. These animals provide a good window into the health of the human environment in which they live.
� Studies have shown that companion animals develop disease as a result of chronic exposure to environmental chemicals such as cancers caused by asbestos (mesothelioma) and herbicides applied to lawns (bladder cancer).
� The latency period for these cancers is significantly shorter for animals than it is for humans. For example, the latency period for mesothelioma in humans and dogs is 30-40 years versus 8-10 years, respectively. In contrast the latency period for acute toxicity caused by lead and herbicides is measured in hours or days and is similar in animals and humans.
� Dogs and cats may be more sensitive to a fixed pathogen dose due to their higher respiratory and metabolic rate than humans.