Bikers, hikers, joggers, equestrians and swimmers regularly recreate along West Marin’s roads and trails and among its open spaces, but they might want to make sure they’re not forgetting to apply sunscreen: the county has a significantly higher incidence of melanoma, a deadly form of skin cancer, than the greater Bay Area, and the mortality rate has increased in recent years, according to a report released last week by the Cancer Prevention Institute of California. Four researchers analyzed data from the California Cancer Registry and found that, though the incidence of melanoma in Marin County was comparable to other regions about a decade ago, the rate has quadrupled in the past decade. That makes it 43 percent higher than the greater Bay Area rate and 60 percent higher than the state average excluding the Bay Area. The high incidence rate and its recent increase can in part be explained by better reporting to the registry, and the data show that a slightly higher percentage of cases in Marin are caught in earlier stages than in the Bay Area, indicating better screening. But the report said it was “unlikely” that changes in reporting could completely explain the shift and that early detection still meant there were more overall cases. “We see some evidence, in a good way, that there is a higher proportion that are caught thinner and earlier. That suggests better access to screening, or better screening itself. But these are all melanoma… these are real diagnoses,” said Christina Clarke, an author of the paper and a research scientist at the institute. The five-year mortality rate in the county also rose 18 percent between 2002-2006 and 2007-2011, while the greater Bay Area and California at large did not see a similar increase. Though Marin’s small population makes statistical analysis more difficult, the report still said the jump was significant. As for the reasons that Marin’s population might be at risk, in addition to age and race (we are largely white and older), Marin’s residents are known for being active in the outdoors, and intermittent, intense exposure is a big risk factor. “[People in Marin] probably have a lifelong history of getting exposure,” Dr. Clarke said, adding that fog “doesn’t mean there’s no U.V.” Americans have lackluster rates of sunscreen use, with just a third of people reporting that they regularly use the product, according to national surveys funded by the Center for Disease Control. (Fifty-eight percent used at least one of three methods to protect themselves, which also included seeking shade and wearing protective clothing.) Hopefully, too, there will soon be more sunscreen options on the market; this week the House of Representatives passed the Sunscreen Innovation Act, which sets deadlines for the Food and Drug Administration to review new sunscreen ingredients that have been approved for years in Europe.