Half the Hispanics in the United States live in counties that frequently violate air pollution standards and are therefore exposed to a greater risk of breathing polluted or harmful air, according to a new study.

The report, "U.S. Latinos and Air Pollution: A Call to Action," was produced by the National Latino Coalition on Climate Change, Natural Resources Defense Council, the Center for American Progress and the National Wildlife Federation.

The document emphasizes the high levels of environmental pollution in the states where more than 75 percent of Latinos live: Arizona, California, Colorado, Florida, Illinois, Massachusetts, Nevada, New Jersey, New York, Pennsylvania and Texas.

Hispanics are the largest minority in the 191 metropolitan districts "with the highest expansion in areas of concentrated vehicle traffic, industry, and power plant activity," the study says.

A large number of those Hispanics do not have health insurance, according to the report, and exposure to air pollution "can aggravate preexisting health problems - especially respiratory problems like asthma."

In 2008, about 4.7 million Hispanics had been diagnosed by a physician with asthma, and Latinos have three times the chance of dying from that illness as other racial or ethnic groups do, the study notes.

Along those lines, the NRDC criticized the recent decision by President Barack Obama to block plans to tighten the ozone standards maintained by the Environmental Protection Agency.

That measure left hundreds of thousands of people facing an unacceptable level of risk regarding the air they breathe, the report says.

Meanwhile, the mercury rule now under consideration by the EPA "is critical to public health and would protect the nearly 40 percent of Latinos living within 30 miles of a power plant," the study states.