He has focused on reducing the level of children's exposure to lead and pesticides and has participated in the World Health Organization's global campaign to eradicate smallpox.

[5] Additionally, from 1995 to 1997, Landrigan served on the Presidential Advisory Committee on Gulf War Veteran's Illnesses,[6] and, in 1997 and 1998, served as Senior Advisor on Children's Health to the Administrator of the U.S. Environmental Protection Agency, where he helped establish the Office of Children's Health Protection.

In testing the blood of children attending schools near ASARCO's El Paso smelting plant, Landrigan concluded that 60% of children living within one mile of the smelter had elevated blood lead levels and that even small amounts of lead exposure lowers a child's IQ.

On February 11, 2002, Landrigan testified before the House Committee on Education and the Workforce on the impacts of the September 11 attacks on the health of children.

"[5]In October 2001, New York Magazine noted disagreement between Landrigan and the EPA over the dangers posed by asbestos particles found in the air immediately after the September 11 attacks.

While generally agreeing that significant risk was to the rescue workers alone,[13] Landrigan disagreed with the EPA that tiny asbestos particles were too small to be considered dangerous, saying, "It's been substantiated by 30 or 40 years of research that the smaller fibers are the ones that can penetrate most deeply into the lungs.

From 1996 to 2005, Landrigan served in the Medical Corps of the United States Naval Reserve, retiring at the rank of Captain.