SEATTLE — Dozens of government officials and researchers from a half-dozen U.S. states and a few countries that have legalized marijuana or are at least thinking about it are gathering in Washington this week for meetings focused largely on one question: How do we know if it’s working?

Organizers say it’s crucial to get a better handle on what data are being collected about the impacts of legalization and to consider what further research is needed. Otherwise, it’s going to be tough to quantify how this major social policy change is affecting everything from school suspension rates to traffic fatalities.

“The real purpose … is to be sure we’re doing the best we can to evaluate the impacts,” said John Walsh, with the Washington Office on Latin America, a social-justice organization sponsoring the conference along with the Washington state chapter of the American Civil Liberties Union. “We want to learn from the pioneers for the pioneers, but be more systematic about what we know and what we still need to learn so the jurisdictions that are coming next can avoid mistakes and do an even better job.”

The conference, held in Seattle and Spokane, has drawn officials from the legal pot states of Washington, Colorado, Oregon and Alaska, as well as Vermont and California, which is expected to vote on legalization next year. Other attendees have come from Jamaica, Mexico, Colombia and Uruguay, the only country that has legalized the adult use of marijuana.

Some data tracked

Washington’s legal pot law, passed in 2012, included a requirement that the state conduct a cost-benefit analysis, and some data are being tracked and analyzed, including on marijuana-involved traffic stops, marijuana-related calls to the state poison center and admissions to addiction treatment centers. Surveys provide a good idea of students’ attitudes toward and use of marijuana, and the University of Washington is assessing marijuana-related parenting behaviors to better inform prevention efforts.

In Colorado, the only other state where legal, recreational pot sales have started, officials are also tracking marijuana-related school suspensions, hospital room marijuana mentions, impaired driving cases and poison control calls.

But there are shortcomings, too, as Dr. Kathy Lofy, Washington’s top public health officer, wrote in notes for the conference. Health-risk behavior surveys are of limited use when it comes to estimating marijuana use in small areas or among ethnic groups; it’s not clear how to identify marijuana-related car accidents; there’s limited data available on long-term marijuana use; and there’s no national consensus yet about how to survey people about changing ways of using pot, such as by vaporizing it or eating it.

Vital messages

The conference also provided a chance for attendees to chat about what has and hasn’t worked well in Washington, Colorado and Uruguay.

Dr. Jay Butler, the public health director in Alaska, which joined Oregon in voting to legalize pot last year, said in response to a conference questionnaire that he wanted to learn more about the legal markets that are already up and running. And Conrad Gregory, the chief economic development consultant for California Lt. Gov. Gavin Newsom, said he was interested in ideas for how to incorporate the growers in that state’s famed “Emerald Triangle” into any statewide legal marijuana industry, should California vote to legalize.

Dr. Wendel Abel, who serves on the agency that has been set up to regulate medical marijuana in Jamaica, noted that governments need to carefully craft messages for young people saying that just because marijuana’s legal doesn’t mean it’s not harmful — something public health advocates said Washington failed to do before legal sales began.

But he said he was also struck by the economic possibilities on seeing that recreational sales in Washington and Colorado have topped a combined $500 million, with tens of millions of dollars in tax revenue coming into state coffers.

“You’re able to divert funds that would have gone into the black market,” he said. “This is attractive.”