In order to assess the lifetime risk of skin cancer for recreational users from dermal exposure to polycyclic aromatic hydrocarbons (PAHs), sediment samples were collected from beach sites along the St. Marys River near Sault Ste. Marie, Ontario, and in Hamilton Harbor and Toronto Harbor, Ontario, and analyzed for PAHs. Dermal exposure and lifetime skin cancer risk were estimated as follows: Concentrations of 11 PAHs with sufficient or limited evidence of carcinogenicity or mutagenicity were converted to benzo(a)pyrene (BaP) equivalents using toxic equivalency factors (TEFs). Lifetime dermal exposure values were derived based on the BaP equivalents in the silt + clay fraction taken as representative of suspended sediment particulates to which recreational users would be exposed. The lifetime health risk of skin cancer associated with such exposures was above the negligible risk level of 1.0 x 10(-6) at offshore Rytac, Lake George Channel, and Bell Point beaches in the St. Marys River; at Pier 4 Park in Hamilton Harbor; and at Humber Bay, Sunnyside Beach, Cherry Beach, and Water Rats Sailing Club in Toronto Harbor. Risk was negligible inshore at the Rytac and Bell Point beaches and at Squirrel Island and Ojibway Trailer Park along St. Marys River, at Lax Beach in Hamilton Harbor; and at Centre Island in Toronto Harbor. Strategies to reduce risk were developed with these communities; a key recommendation was to take a bath or shower within 24 h after a swim because virtually all the PAHs on the skin would be removed.