The Environmental Protection Agency has awarded $7 million in grants to researchers to study the cumulative health impact of pollutants like mercury and lead and social factors like stress and poor nutrition in several low-income communities, the agency said Tuesday. The E.P.A. typically studies only the health effects of individual chemicals. But a  suggests that cumulative exposure to multiple pollutants, and nonchemical factors like stress, poverty and poor diet, can amplify the negative effects of a single toxic substance. Several studies will also examine why some ethnicities and subgroups appear more susceptible to environmental health threats, like asthma, than others.

Minority, low-income and tribal populations are disproportionately exposed to and affected by pollution, as environmental justice advocates have noted for decades. The research grants are part of a commitment made by the agency in 2010 to better address these disproportionate impacts, Paul Anastas, assistant administrator for the E.P.A. Office of Research and Development, said in a statement.

“This research could pave the way for more interdisciplinary work that is responsive to community concerns and environmental justice,” Dr. Anastas, a chemist, said.

In 2010, the E.P.A.’s administrator, Lisa P. Jackson, made addressing lingering issues of environmental justice one of her top priorities.

In an interview with the Washington Post in November, she said that reaching out to the neglected communities that remain “hot spots” of emissions and contamination was “the biggest chunk of unfinished business when you think about the environmental landscape.”

Last year, the E.P.A. unveiled a plan to integrate environmental justice concerns into the agency’s rule-making and permitting process, and in December, the agency played host to the first White House Forum on Environmental Justice, inviting dozens of community and grassroots leaders to participate.

Some activists were tired of talk and study and ready for action, however.

“We need to stop being studied to death,” Suzie Canales, co-founder of a Corpus Christi grassroots environmental group, told Ms. Jackson at the forum, according to Greenwire.

Later, speaking to the assembled forum, Ms. Canales disparaged the E.P.A’s new environmental justice road map.

“These are bureaucratic words on paper,” she said. “They do nothing for these communities.”

In an interview to be published Friday in an E.P.A. newsletter, Devon Payne-Sturges, an environmental health scientist with the agency’s Office of Children’s Health Protection, acknowledged the tension between the E.P.A. and activists. But she said the agency was working to address that frustration, and at a more recent symposium on environmental justice, some grassroots leaders began to see the value of intensive study before major action is taken.

“Those of us here at E.P.A. know we have to have evidence and data to support our actions because they can be challenged,” Dr. Payne-Sturges, who has a doctorate in environmental health sciences, said. “I think the community representatives began to recognize that you need good analytical tools, information, and the science.”