News

Should exposure to air pollution be considered a risk factor for heart disease, just like elevated levels of cholesterol?

In recent years, a growing body of medical evidence has implicated fumes from car tailpipes and industrial smokestacks in heart attacks and strokes. In fact, hospital admissions for a slew of ailments tend to surge on smoggy days.

Now, a team of California researchers has completed a study that shows precisely how bad air could be wreaking havoc on the body.

In lab experiments, they exposed blood vessel cells to diesel exhaust particles. The mix produced an inflammatory response - the first step on the road to heart disease.

Diesel particles are coated with a variety of potentially harmful chemicals, including organic hydrocarbons and molecularly unstable transitional metals, said lead researcher André Nel of the University of California, Los Angeles.

In particular, these particles appear to trigger the production of free radicals that can damage tissues and cause the formation of plaque in blood vessels.

Dr. Nel said the pollution-induced inflammation could be contributing to a buildup of fatty plaque deposits from other sources, further narrowing blood vessels. If the plaque ruptures, it could form a clot and block blood flow, triggering a heart attack or stroke.

As part of the study, the researchers also exposed caged mice to automobile exhaust by placing them along a highway. The findings, published in the journal Genome Biology, revealed that air pollution activated many different genes involved in inflammation in the mice.

Dr. Nel suggested that genetic studies may eventually find that some people are more susceptible to the harmful effects of air pollution than others.

"Our results emphasize the importance of controlling air pollution as another tool for preventing cardiovascular disease," said Ke Wei Gong, who was part of the research team.

Hold the antibiotics

Giving children antibiotics to prevent urinary tract infections won't stop the painful episodes from recurring and may increase the chances of getting a drug-resistant strain, U.S. researchers warn.

Some kids - especially girls - are prone to frequent urinary tract infections. To stop the bacterial infections before they start again, some doctors prescribe antibiotics.

But a new study has found that children who take antibiotics on a continuing basis are just as likely to have flare-ups as those who aren't taking the drugs. Even worse, the medicated kids are seven times more likely to develop a drug-resistant strain, according to the findings published in The Journal of the American Medical Association.

Children who get a drug-resistant strain often need to take even more powerful antibiotics to bring the infection under control, said Patrick Conway, who led the study at the University of Pennsylvania in Philadelphia. Some of them must be hospitalized to receive the treatment intravenously.

For years, experts have been warning about the dangers of overprescribing antibiotics. They advocate alternative approaches such as the use of probiotics - "friendly" bacteria that can keep the bad ones in check.

Sunning away MS

Canada has one of the highest rates of multiple sclerosis in the world. A new study of twins provides more evidence that a lack of sunlight could be a culprit.

Researchers surveyed 79 pairs of identical twins with a family history of MS. The twins were asked which one spent more time sun tanning, going to the beach and playing team sports as a child. The results revealed that the twin who spent more hours outdoors had a 25- to 57-per-cent lower chance of developing MS as an adult than the indoor-bound sibling did.

This is not the first time a lack of sunlight has been linked to MS. But the fact that the study involved twins, who essentially share the same genetic makeup, helps to bolster the case that "sun exposure appears to have a protective effect," said Thomas Mack, one of the researchers at the Keck School of Medicine at the University of Southern California.

Sunlight causes skin to produce vitamin D, which plays a role in the prevention of other diseases. The sun can also affect the immune system. "There are a lot of links that need to be explored," Dr. Mack said.

Tonsils, an AIDS gateway?

Medical experts are calling for more men to be circumcised as a way of slowing the spread of AIDS. Could tonsillectomies be next?

HIV, the virus that causes AIDS, is spread mainly through sexual contact. The virus tends to latch on to receptors on mucosal surfaces, using them as gateways into the body.

In the case of oral sex, the mucosal surfaces inside the mouth are fairly thick, which provides some defence against the deadly virus. As well, saliva contains microbe-combatting cells.

However, the tonsils may still be "easily accessible to HIV," warn researchers at the U.S. National Institute of Dental and Craniofacial Research in Bethesda, Md.

They conducted a study that found the tonsils - two pink lumps of lymphoid tissue on either side of the throat - contain exposed "molecules that may bind and entrap HIV." Even worse, the tonsils don't seem to have the same level of immune protection as the rest of the mouth and throat, according to the findings published in The American Journal of Pathology.

The researchers conclude that tonsils are "a potential site for oral transmission" and called for more study of the risk.

ptaylor@globeandmail.com