According to a report released Monday that details marijuana possession arrest rates in the United States from 2001 to 2010, the District of Columbia and Maryland are leading the nation in arrest rates for marijuana possession, and marijuana possession laws are disproportionately enforced against blacks.

D.C. had the country’s highest arrest rate for marijuana possession (846 per 100,000) — more than three times greater than the national rate (256 per 100,000) — and Maryland had the fourth highest arrest rate (409 per 100,000) in 2010. Worcester County had the highest rate of any county nationwide (2,132 per 100,000), and Baltimore City had the fifth highest rate (1,136 per 100,000).

“Marijuana prohibition is taking a toll on the entire country, but Washington, D.C., and Maryland are among the states paying the biggest price,” said Mason Tvert, director of communications for the Marijuana Policy Project. “Law enforcement resources would be better spent addressing serious crimes instead of arresting adults for using a substance objectively less harmful than alcohol.”

Researchers also found that blacks accounted for 91 percent of marijuana possession arrests in D.C., and blacks were more than eight times more likely to be arrested for marijuana possession than whites. In Maryland, blacks accounted for 58 percent of marijuana possession arrests and were more than three times more likely to be arrested. In Baltimore City, blacks were arrested for marijuana possession at more than five-and-half times the rate of whites. Nationwide, whites and blacks use marijuana at comparable rates, according to the Substance Abuse and Mental Health Services Administration. The report does not provide Latino arrest rates because federal arrest statistics do not distinguish between white and Latino arrests.

“Marijuana prohibition laws are not only irrational, but also unfair,” Tvert said. “Discrimination against communities of color played a role in their creation, and it continues to play a role in their enforcement.”