The American Petroleum Institute is the largest U.S. trade association for the oil and natural gas industry. It claims to represent nearly 600 corporations involved in production, refinement, distribution, and many other aspects of the petroleum industry. Much of its work has been dedicated to the advancement of climate change denial and blocking of climate legislation to defend the interests of its constituent organizations. The association describes its mission as "to promote safety across the industry globally and influence public policy in support of a strong, viable U.S. oil and natural gas industry". API's chief functions on behalf of the industry include advocacy, negotiation and lobbying with governmental, legal, and regulatory agencies; research into economic, toxicological, and environmental effects; establishment and certification of industry standards; and education outreach. API both funds and conducts research related to many aspects of the petroleum industry.