Answer;
-An internal report by the Environmental Protection Agency (EPA)
Step-by-step explanation;
-Environmental Protection Agency (EPA) is an agency of the U.S. government that sets and enforces national pollution-control standards. Its purpose is ensure that all Americans are protected from significant risks to human health and the environment where they live, learn and work, also federal laws protecting human health and the environment are enforced fairly and effectively, among other roles.
Therefore; an internal report by the Environmental Protection Agency (EPA), is more likely to be the most valid source of information about pollution, since it is the body that is tasked by ensuring that all Americans are protected from the effects of pollution and also governs the federal laws protecting human health.