Toxic chemicals from coal-tar enter Lake Champlain through water runoff from developed areas. Coal-tar is often found in driveway and parking lot sealants, and has been linked to PAH (polyaromatic hydrocarbons) contamination in waters around the nation.
When waterways and waterbodies are polluted with coal-tar, PAH levels tend to be higher than those in waters without coal-tar sealants surrounding them. Studies have shown that PAHs are toxic to amphibians, and likely other wildife and humans. For example, amphibians frequently die or have their growth stunted when in contact with PAHs (read one study here). Coal-tar has also been linked to PAHs in apartment and house floor dust, where coal-tar flakes are tracked indoors by shoes, bike tires, and pets' feet. Since PAHs are a known human carcinogen (read about it here), PAH in floor dust can be toxic to children, adults, and pets.