LOS ANGELES — Scott Svonkin joined the Los Angeles County Commission on Insurance 10 years ago because he was concerned about an emerging problem: people losing health coverage. Since then, the ranks of uninsured Americans have swelled to more than 46 million.

Svonkin almost became one of them.

It happened after he left a comfortable government job as a legislative chief of staff to start his own marketing and public affairs consulting business. Late last year he started shopping around for health insurance for himself, his expectant wife and his young daughter.

He knew he'd pay more without an employer picking up most of the tab. And he knew he'd have to fill out a medical questionnaire because, unlike job-based coverage, individual insurance in California is contingent on an applicant's health. But that didn't concern him because, he said, "I'm healthy as a horse, never smoked and have had no major surgery."

As it turned out, Svonkin was rejected by not just one but three of California's biggest health insurers, which cited his history of asthma, among other things.

"I couldn't buy it at any price," said Svonkin, 40. "I remember thinking, 'This can't be happening to me.' "

Svonkin is part of what experts say is a largely hidden aspect of the U.S. health insurance crisis: the uninsurables, people whom insurance companies won't touch, even though they can afford to pay high premiums. Some, such as Svonkin, pay steep rates for lean coverage from the state's high-risk insurance pool. Others simply go without.

Insurers have wide latitude to choose among applicants for individual coverage and set premiums based on medical conditions. Insurers say medical underwriting, as the selection process is known, is key to keeping premiums under control.

Consumer advocates see the practice as cherry-picking — a legal form of discrimination that is no longer tolerated in schools, public accommodations or workplaces — and a way to guarantee profits.

"The idea is to avoid all risk," said Bryan Liang, director of the Institute of Health Law Studies at California Western School of Law in San Diego.

Jerry Flanagan, an advocate with the Foundation for Consumer and Taxpayer Rights, said it wouldn't take much to be left out of the private-insurance market. "A minor asthma condition or a surgery 10 years ago that requires no further medical care is enough to get you blacklisted forever," he said.

As a result, some people forgo treatment so as not to tarnish their health records. Others withhold information from doctors or ask them to leave details out of their records. For those who are uninsurable, healthcare often is the chief reason they stay in or take a certain job.

Uninsurable individuals pose a significant challenge for the state, which expects to spend more than $10 billion this year on people who lack adequate coverage.

A consumer survey this year found that 1 in 5 people who applied for individual coverage was turned away or charged a higher premium because of pre-existing conditions.

The industry contends that individual coverage is widely available. But experts say a wave of consolidation has reduced the number of insurers offering individual coverage, leaving a marketplace that shuns all but the ostensibly healthiest consumers.

Insurers say they are picky because they have to be.

Kaiser Permanente's "fairly generous" benefits require that the health maintenance organization be restrictive to remain solvent, spokesman Jim Anderson said. "We have to be very careful to not enroll a bunch of people who are going to spend all the money on their care."

Insurers declined to disclose the underwriting guidelines that lead to rejection or higher premiums. But a review of public records, as well as rejection letters sent to individuals, shows that California carriers turn people away or charge them higher premiums for conditions that range from the catastrophic to the common. Cancer, epilepsy and AIDS make the list, along with breast implants, ear infections, varicose veins and sleep apnea.

Jeffrey Miles, a vice president of the California Association of Health Underwriters, a trade group for independent insurance agents, said one of his clients — a 27-year-old woman "in perfect health with absolutely nothing wrong" — was rejected because she had seen a psychologist for three months after breaking up with a boyfriend.

Consumer advocates say out-of-date, ambiguous and even erroneous medical information can render people uninsurable. Sometimes the reasons can seem absurd. In a recent letter to an otherwise healthy college graduate, for instance, Blue Cross listed among the reasons it denied coverage a past bout of jock itch, "successfully treated with cream."

A last resort for people turned away by the private market is the state's high-risk pool, in which the state assumes the financial risk but pays private insurers to administer coverage. Enrollees spend as much as one-third of their income on monthly premiums that range as high as $796. Yet annual benefits are capped at $75,000.

Blue Shield declined to discuss Svonkin's case, citing privacy laws, as did other insurers that subsequently rejected him, Blue Cross and PacifiCare. Although the rejection notices pointed to various problems — "expectant fatherhood" and swelling from a spider bite — all three blamed his history of asthma.

Svonkin was able to enroll his wife, daughter and baby son in a private plan. He reluctantly enrolled himself in the state's high-risk pool. In an ironic twist, the pool assigned him to a plan administered by Blue Shield. His premiums are $479 a month — far more than he figures he has cost the plan. The only medical expenses he has submitted in his first year on the plan have been his prescriptions, which retail for about $100 a month.