WASHINGTON — The Environmental Protection Agency failed to disclose cancer risks to people it exposed to harmful pollutants in research studies, a government watchdog says.

The EPA, which warns of dangers from diesel exhaust and tiny particles in its rules to cut pollution, recruited people for tests on those pollutants in 2010 and 2011. Consent forms they were given didn’t mention cancer because the agency considered the risks minimal, the agency’s Office of Inspector General said Wednesday in a report.

“When justifying a job-killing regulation, EPA argues exposure to particulate matter is deadly, but when they are conducting experiments, they say human exposure studies are not harmful,” Sen. David Vitter, R-La., said in a statement.

The EPA’s test practices have been criticized by Republicans who say the agency contradicts itself in explaining its rules and testing safety. The agency watchdog proposed procedural changes to the EPA’s program, but said “applicable regulations” were followed.

The inspector general rejected Republican demands to halt all human studies.

“The agency should inform study subjects of any potential cancer risks of a pollutant to which they are being exposed,” according to the report, conducted after complaints from federal lawmakers.

The agency pledged to improve its consent forms and set up better plans for reacting to “adverse events and unanticipated problems” in response to the recommendations.

In the past decade, the EPA did 13 studies of particulate matter and four studies on diesel exhaust at its North Carolina laboratory, according to the report. Each study would include 20 to 40 people in a chamber where pollution is set to levels similar to Los Angeles or New York. Blood, heart and lung functions are monitored, the agency said.