Puerto Rico is fast becoming the New Jersey of the Caribbean, resulting in a dramatic increase in air pollution, water pollution and occupational disease, according to Puerto Rican scientific studies.

The extraordinary concentratoin of oil, chemical, pharmaceutical and metals industries on a 100-mile-long tropical island is causing mercury poisoning, respiratory ailments, liver cancer, leukemia and kidney problems among a people already plagued with poverty, Puerto Rican scientists said.

At a conference here on the export of hazardous industries, Dr. Neftalia Garcia of the Mision Industrial de Puerto Rico, an environmental group, said U.S. environmental and occupational health laws are poorly enforced, resulting in "environmental colonialism."

Puerto Rico in the last decade welcomed industry to help combat its 40 percent unemployment rate. But a rash of demonstration in neighborhoods around polluting plants and the recent filing of dozens of lawsuits by sick workers indicates a growing backlash.

"Puerto Rico has been subjected to a colonial pattern of exploitation," said Dr. Richard Levins of the Harvard School of Pulic Health. "A favorable climate for investment is not always a favorable climate for breathing."

Industrial pollution is harming the island's agriculture, he said. For example, smoke enveloping mangrove swamps has killed the birds that eat crop-destroying insects. Fishing grounds have been contaminated by fertilizer factory wastes. Sugar cane yields have declined downwind of industrial plants, Levins told the conference.

Between 1970 and 1974, sulfur dioxide in the air, which causes respiratory illness, increased from 52 to 94 tons per square kilometer of developed land, while it declined in the U.S. from 16 to 14 tons, Garcia said.

Nonetheless, the Puerto Rican Environmental Quality Board, which enforces U.S. laws, recently allowed the Commonwealth Oil Co. to increase the sulfur in fuel it burns from one percent to 1.5 percent.

At Ingenio, a community of about 1,500 near a Union Carbide graphite plant, 51 percent of some 300 people tested last year suffered from respiratory illnesses. Neighborhood residents, who recently picketed to protest the air pollution, also complained that their vegetable gardens and trees have died. Thirteen cases of throat cancer have been diagnosed, Garcia said.

EPA spokesman Frank Napal said, however, "Air pollution is not a major problem in Puerto Rico. Air flow patterns around the island are pretty good. Ninety-five percent of the corporations are in compliance with the law." By contrast, the agency has had some lively fights with sugar refineries and rum distillers over water pollution, he added.

Lawsuits have been filed against a Becton-Dickinson thermometer plant for mercury poisoning which resulted several years ago in 33 workers hospitalized and five deaths, Garcia said, adding that broken thermometers have been thrown in a nearby creek.

Recent protests prevented the location of a proposed Monsanto herbicide plant in Salinas.

Puerto Rica produces 15 percent of the United States' benzene, 28 percent of cyclohexane and 20 percent of para-Xylene -- all major petro-chemicals. Plants such as the Commonwealth Oil Refinery (CORCO) at Penuelas -- the world's largest aromatics facility -- and Union Carbide Caribe have "major health and safety problems," Garcia said.

CORCO workers have complained of nasal and throat cancer, liver cancer, prostate problems, leukemia, lead poisoning, diabetes, hearing loss and respiratory ailments, he added.

Garcia complained that between April 1977 and July 1979, the Occupational Health and Safety Administration conducted only 77 inspections for health problems in Puerto Rico and 1,046 for safety problems, such as machinery maulfunctions.

"And the evidence of health problems is so overwhelming, we don't understand why OSHA has not brought a single court action," he added.

Roger Clark, and OSHA official, said the agency is delegating enforcement to the commonwealth of Puerto Rico.

Puerto Rico also has a major asbestos problem: Five hundred schools and 2,000 public housing units were built with asbestos cement which flakes into microscopic, cancer-causing particles.

With the help of Puerto Rican Legal Services, 27 families have filed suit against the Puerto Rican Housing Department.