US environmental laws and regulations are applicable in Puerto Rico. Land-use planning, overseen by the Puerto Rico Planning Board, is an especially difficult problem, since residential, industrial, and recreational developers are all competing for about 30% of the total land area on an island that is already more densely populated than any state of the US except New Jersey. Pollution from highland latrines and septic systems and from agricultural and industrial wastes is a potential hazard; the rum industry, for example, has traditionally dumped its wastes into the ocean. Moreover, the US requirement that sewage receive secondary treatment before being discharged into deep seas may be unrealistic in view of the commonwealth government's claim, in the late 1970s, that it could not afford to build secondary sewage treatment facilities when 45% of its population lacks primary sewage treatment systems. As of 2003, sewage discharges into the ocean remained a problem: in August 2000, the US Environmental Protection Agency (EPA) granted the Puerto Rico Aqueduct and Sewage Authority's Aguadilla treatment plant a 20-year waiver for discharging primary treated sewage into the ocean, threatening coral reefs.
About 300,000 tons of hazardous waste are generated annually, and 16,000 tons of chemical substances are released into the air, water, and soil each year. In January 1994, 750,000 gallons of oil were spilled off the coast of Puerto Rico, resulting in a fine of over $75 million levied against the three companies responsible. Wetlands on the island have been devastated by development, but in recent years, efforts have been mounted to save and expand these resources.