Dear Doctor: How important is radon as a cause of lung cancer? Should I get my home tested?

Dear Reader: Just a few years ago, radon was the topic of seemingly limitless public and media fascination. Times may have changed, but the presence of radon has not. To answer your question, let's take a closer look at this radioactive element.

A colorless, odorless gas that can be inhaled, radon is produced normally in our environment from the radioactive decay of the elements uranium, radium and thorium. Radon is not a stable element, and its many isotopes are subject to rapid radioactive decay, leading to the release of radioactive particles. This decay also produces solid radioactive elements that can attach to dust particles, which can also be inhaled.

The problem with radon is that exposure to its radioactive particles may lead to cancer, specifically lung cancer. A 2006 study of 59,001 uranium miners followed for 30 years in Germany found a much higher number of lung cancers in those with greater exposure to radon. The highest incidence of lung cancer was seen 15 to 24 years after exposure. Uranium miners in the Colorado Plateau also appear to have an increased risk of lung cancer.

Those who don't mine uranium can't ignore the issue, however. The Iowa Radon Lung Cancer Study, published in 2000, looked at 413 lung cancer cases in Iowa women, ages 40 to 84. The study measured amounts of radon in the homes of those patients who had lived in the same house for more than 20 years. It also measured radon levels in the homes of women with similar ages, smoking histories and work histories who didn't have cancer.

The authors found that 60 percent of the home basements of women with lung cancer exceeded the Environmental Protection Agency limits for radon levels; and 30 percent of the first-floor spaces exceeded those limits. Based on an analysis of radon levels in the control group, the study concluded that increased radon levels led to increased rates of lung cancer.

Subsequently, a combined analysis of 13 European studies evaluated radon levels in the homes of lung cancer patients who had lived there for a minimum of 15 years. For every quantile increase in radon levels, the rate of lung cancer increased by 8.4 percent. Note, however, that smoking played a large part in this increase. When smoking was removed from the equation, the level of increased risk was only 2.3 percent per quantile increase in radon. The authors theorized that, out of all the causes of lung cancer, radon is responsible for 9 percent.

Radon exposure is higher for some people than for others. It enters homes and other buildings through the soil and can build up inside, especially in structures that don't have good ventilation. This is more problematic in winter months when windows are more likely to be closed.

Further, some areas of the country, such as Iowa and the Appalachian Mountains of Pennsylvania, have naturally higher levels of radon. New homes in these areas are constructed to prevent radon from entering and building up inside, and the EPA recommends that all houses be tested. If you're curious about your own area, the EPA has maps showing which zones of the country have more radon.

The take-home message: Radon exposure is considered a substantial risk factor for lung cancer. If you live in a part of the country where radon levels are high, you should have your home tested.

Dear Doctor: Could boxed macaroni and cheese really be as bad for you as news reports suggest? Sometimes, that's all my kids will eat.

Dear Reader: The recent news about the presence of chemicals called phthalates in boxed macaroni and cheese sent a shockwave through many American kitchens. Affordable, easy to prepare and beloved by the younger (and let's face it, more than a few of the older) members of the family, pre-packaged mac and cheese has become a mealtime staple.

However, a study funded by an advocacy group called the Coalition for Safer Food Processing and Packaging raised an alarm earlier this year. Testing for phthalates -- a family of chemicals used, among other things, to make plastics flexible -- the group reported measurable amounts in 29 of the 30 cheese products. These include boxed macaroni and cheese, as well as soft, hard and natural cheeses.

Concentrations ranged from 0.6 parts per billion to 295 parts per billion, with the lowest in natural cheeses. The highest were found in cheese packets in boxed mac and cheese. In all cases the phthalates migrated into the food via the packaging.

The chemicals, many of which were banned from use in infants' and children's products in 2008, are known as endocrine disrupters. That is, they interfere with the working of the body's hormonal system. Exposure in high amounts can affect fertility in adults, and is associated with disruptive behavior in children.

All of this sounds quite alarming. But before you banish all cheese products from your home, let's take a closer look. The concentration at which phthalates begins to cause problems is not known. Yet the study labels the 0.6 parts per billion to 295 parts per billion of phthalates that were found in the tested products as a "high amount." Additionally, the Centers for Disease Control and Prevention have found that, although we encounter phthalates in a variety of products, combined exposure remains extremely low.

To be honest, we think if you're going to be worried about the health effects of boxed mac and cheese, all you really need to do is read the sodium level on the nutrition label. And while mac and cheese out of a box is easy, sooner or later, for your children's long-term health, you'll have to bring fruit, veggies and other building blocks of a healthful diet into the mix.

Maybe start by making the boxed mac and cheese a special treat on a certain day of the week. Or find a recipe the family likes and make mac and cheese from scratch. It may not be as fast, but it's far more healthful. And, yes, we know these changes aren't easy. As parents ourselves, we face the same challenges of pleasing a picky eater's palate.

A final word: If the mac and cheese study has you worried about phthalates in general, take steps to cut them out of your food chain. Never use plastic in the microwave, as the heat can cause the chemical to move into your food. The same goes for the dishwasher -- wash any plastic ware by hand. For the greatest peace of mind, skip the plastic ware altogether and switch your food storage to glass or stainless steel.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My grandmother has a daughter and a son with Huntington's disease, and her husband and a few of her in-laws passed away from it. What can you tell us about this terrible disease? Who in the family could yet develop it?

Dear Reader: "Terrible" is the correct description of Huntington's disease. It's a rare genetic disease -- affecting about 5.7 out of 100,000 people in Europe, Australia and North America -- but it's unrelenting and eventually leads to death.

Almost everyone with Huntington's carries a disease-causing mutated gene on one chromosome and a normal copy on the other chromosome. That means their children have a 50/50 chance of having the mutated chromosome passed down to them. Unfortunately, in Huntington's, the mutated gene is dominant. So, even if a person has only one of the abnormal genes, he or she will develop the disease. So, to answer your question about the potential for other family members, any children of your grandmother's daughter and son with the disease have a 50/50 chance of developing it as well.

In the rare cases in which a person has two copies of the Huntington's gene, he or she will without doubt pass the disease on to all their children. Further, children who get the gene from their father are more likely to develop the disease earlier in life and to experience a more rapid deterioration.

Here's what happens: The mutant gene in Huntington's disease produces an abnormal protein that damages both the nucleus and other components of nerve cells, killing them. The nerve death is especially severe in the area of the brain called the striatum. These changes can be detected via MRI between nine and 20 years before a patient shows symptoms, which typically occur between the ages of 35 and 44.

The first sign of Huntington's disease is an involuntary movement abnormality termed chorea. Initially, this may be perceived as restlessness or lack of coordination. When it worsens, movements become random, jerky and uncontrollable, making it difficult for a person even to hold his or her posture or maintain a sustained motor action such as sticking out the tongue.

Psychiatric symptoms of depression and irritability, which can occur at any time during the disease, may be noticeable even before the onset of chorea. An estimated 33 to 76 percent of patients report anxiety, depression or apathy during the course of their illness. Three to 11 percent report symptoms of psychosis, including hallucinations, delusions and paranoia.

It gets worse. Patients' cognitive abilities are affected as well, leading to difficulty making decisions, multitasking or switching from one mental activity to another. Eventually, the memory problems lead to dementia.

In the latter stages of the disease, people may develop a rigid muscular state similar to Parkinson's. This can lead to the inability to walk. People can also experience weight loss, vision disturbances, and difficulty swallowing and breathing. The progression is prolonged, with death generally occurring 20 years after onset of symptoms.

Although genetic testing can easily diagnose the Huntington's mutation, the availability of such testing is relatively recent. Further, while it can guide decisions about whether or not to have children, it can do nothing to change the current reality. My heart goes out to your grandmother and the rest of your family.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)