WASHINGTON — Sen. Dianne Feinstein on Wednesday joined Gov. Jerry Brown in expressing skepticism about legalizing marijuana in California for recreational purposes.

The state’s senior senator said that one of her concerns is the potential for pot-impaired drivers to take to the road. Feinstein said she hopes California declines to join Colorado and Washington in approving the sale of marijuana for recreational use.

“The risk of people using marijuana and driving is very substantial,” she said.

As a possible example, the California Highway Patrol is investigating a fatal weekend collision in Santa Rosa as being related to marijuana use. A woman and her daughter-in-law were killed when a Toyota Camry in which they were riding was rear-ended by a pickup truck. A preliminary CHP investigation determined that the 30-year-old man driving the pickup was impaired by marijuana and reading a text message on his cellphone at the time of the collision.

California became the first state to legalize the use of marijuana for medicinal purposes in 1996, but voters rejected a ballot initiative seeking to legalize it for recreational purposes in 2010. The margin of defeat was relatively narrow, 54 percent to 46 percent, and public opinion appears to have softened since then.

A Public Policy Institute of California poll taken last September found a majority of Californians supporting full legalization for the first time, with 52 percent of all adults and 60 percent of likely voters in favor.

Feinstein said in the interview that she believes California has gone as far as is responsible in allowing marijuana to be sold for medical purposes. She said serving on the California Women’s Board of Terms and Parole during the 1960s allowed her to see how marijuana, in her view, led to bigger problems for many female inmates.

She also said she did not understand how culture is improved through legalizing marijuana. Earlier this month, Brown said on NBC’s “Meet the Press” that if marijuana use gains legitimacy through full legalization “how many people can get stoned and still have a great state or a great nation?”

Despite such criticism, the movement to expand full legalization beyond Colorado and Washington is continuing. A Gallup poll taken last year found that 58 percent of Americans say the drug should be legalized. Several legalization petitions are circulating this year in California, although none has yet qualified for a ballot.

Meanwhile, California Lt. Gov. Gavin Newsom supports legalization of marijuana and is leading a panel of medical and law enforcement officials who are studying how the state could tax and regulate marijuana sales effectively.