The environment modern America created for itself may now be a leading cause of death in the United States, a new government report said yesterday.

It said that even though the nation spent $207 million last year researching the links between pollution and cancer, heart and lung disease, not enough is being done in terms of preventive health to bring down the death toll from those killers.

Cancer, heart and lung disease, "linked by growing evidence to environmental causes, have become the leading causes of mortality in our society," the Environmental Protection Agency said in releasing the report.

"The extent of illness, death and costs to society from environmentally related cancer and heart and lung disease is a matter of national concern," said EPA Administrator Douglas Costle.

"Changes in our level of effort will be necessary to reduce the risk and occurrence of these diseases."

The report was prepared by a federal task force chaired by Costle and composed of representatives from EPA, the National Cancer Institute, the National Heart, Lung and Blood Institute, the National Institute for Occupational Safety and Health and the National Institute of Environmental Health Sciences.

Their report states:

"The environment we have created may now be a major cause of death in the United States. Cancer, heart and lung disease, accounting for 12 percent of deaths in 1900 and 38 percent in 1940, were the cause of 59 percent of all deaths in 1976."

Part of that change, it said, stems from the success of modern medicine in reducing the toll from accidents and such scourges as tuberculosis.

But it adds, "Growing evidence links much of the occurrence of these disease (cancer, heart and lung) to the nature of the environment."

The report notes that lung cancer rates have risen rapidly in the past 30 years and says, "It is postulated that a part of the increase can be attributed to environmental factors other than smoking."

It also says about 30 percent of all Americans now die of cancer, but only 6,000 of the 100,000 chemicals that have poisonous properties have been tested for cancer-causing potential.

Heart disease rates are known to the higher in areas of high air pollution, the study adds, and while a direct cause may be difficult to prove there is speculation that bad air may aggravate heart conditions.

Respiratory diseases, including emphysema, bronchitis, pneumonitis and asthma are now the sixth most prevalent cause of death in the country, and pollution contributes to the illnesses, it said.