It's a conundrum that puzzles doctors and patients alike: one person smokes a few cigarettes per week in college and contracts lung cancer in middle age, while another person smokes a pack a day his whole life -- and lives to age 90.

A new program announced last week by the National Institutes of Health aims to unravel such mysteries by precisely measuring the role that environmental agents, such as pesticides and solvents, play in common diseases, including cancer, asthma, and autism.

A major part of the program will fund the development of technologies to monitor personal environmental exposures and to determine how those exposures interact with an individual's genetic makeup to increase the risk for disease. Scientists hope these technologies will allow doctors to determine who is at risk early on, and thus be able to intervene soon enough to prevent serious damage.

The NIH has designated $88 million for the period 2007-10 to fund research both inside and outside the institute. The money will go toward development of wearable sensors that measure exposure to environmental toxins, such as solvents, pesticides, and heavy metals.

The funds will also support the development of sensors to determine if exposure to toxins triggers biochemical pathways linked to disease, such as inflammation or cell death, in some individuals. Ultimately, these technologies will be incorporated into genetic studies to understand the link between genes, the environment, and disease.

Initially, the sensors would be used in population studies of disease. But David Schwartz, director of the National Institute of Environmental Health Sciences (part of the NIH), envisions a day when everyone would wear a sensor that measured levels of key chemicals. An individual's doctor could then read the information and determine if the patient had been exposed to chemicals and therefore was at risk of developing a disease.

The role of environmental toxins in human disease and death has been a major issue in both the public health and legal arenas. Scientists often have difficulty determining if a reported increase in disease, such as a cancer cluster, is linked to a specific factor in the environment. Emerging technologies that could accurately measure exposure and individual response to different chemicals could clarify these often contentious cases.