I woke up early last Saturday so I could pick out paint for my living room. It turns out a lot has changed in the world of paint.

The last time I did this, it was hard enough choosing between bittersweet chocolate and black mahogany. These days color is the least of my worries. I now have to worry about how many volatile organic compounds, or VOCs, I’m willing to tolerate in my paint. In fact, the paint department has nearly tripled in size, as virtually all the colors are available in no-VOC, low-VOC and the old-fashioned version, which I can only assume is chockablock with VOCs.

I later found out it’s not just paint. There are VOCs in air fresheners, markers, furniture, printers . . . . It made me want to stop breathing altogether.

So how many of them are out there? And how worried should I be about inhaling a few of them? And what, exactly, is a VOC, anyway?

A volatile organic compound is a carbon-containing chemical likely to exist in a gaseous state at room temperature under normal atmospheric pressure conditions. This is an enormous category, and many volatile organic compounds don’t seem to pose any health risk at everyday concentrations. Foods, for example, are full of VOCs. In fact, if you can smell a food at room temperature, that’s a pretty good indication that it’s giving off VOCs.

When public-health advocates talk about volatile organic compounds, they don’t mean the stuff in basil or mangoes. They’re referring to a subset of the class that has been shown to negatively affect human health in various ways. Some are suspected carcinogens, others irritate the airways and eyes, and a few may threaten the nervous system. They are a health concern in the air and the public drinking supply.

You’d probably recognize some dangerous volatile organic compounds by name. Formaldehyde, a nauseatingly smelly chemical, is a classic example. But many of them have complex chemical names that you’d never recognize, such as 1,3-butadiene.

Air quality experts have been talking about volatile organic compounds for at least 25 years. Some readers may be familiar with the term “sick building syndrome,” which involved new or remodeled buildings that caused their occupants to develop itchy or watery eyes, difficulty breathing, dizziness, itchy skin and a variety of other ailments.

These effects are the result of what scientists call off-gassing, which is what happens when objects release gases into the air. Paint tends to off-gas, as do construction materials and furnishings. This became a particular problem in the 1970s and 1980s, when builders began dramatically reducing ventilation in new buildings to improve energy efficiency. Building guidelines have since been revised to improve air circulation, but some public-health advocates believe that we’re still being exposed to unhealthful levels of some chemicals.

And here we get to the real problem in the field of toxicology. There are often alarming reports of evidence that a chemical is carcinogenic, neurotoxic, endocrine-disruptive or otherwise dangerous to health. Based on these stories, it’s tempting to view chemicals as either good, like vitamins and minerals, or bad, like preservatives and industrial compounds.

But toxicologists have a saying that everyone should know: The dose makes the poison. In other words, everything is dangerous if you consume enough of it. Even water can — and, on occasion, does — kill people who drink an excessive amount.

The challenge is figuring out how much of a particular substance a person can tolerate before they’re at risk of getting sick. For acute health effects, it’s pretty easy to figure this out. If you’re painting your living room and your eyes start to water or you’re having trouble breathing, ventilation is inadequate.

For diseases that develop more slowly, determining toxic doses is challenging. Since it’s both impractical and unethical to intentionally give people cancer for the sake of research, scientists have to rely on a variety of studies of varying reliability.

Cohort studies — in which epidemiologists follow one group that is exposed to the chemical under study and another that is not to see who develops cancer — are the best available. They work great for subjects such as cigarette smoking, because it’s easy to measure the frequency with which someone smokes. For environmental exposures such as contact with volatile organic compounds, these studies are much rarer. The concentration of paint fumes in your house is difficult to measure and changes over time.

Another option is the case-control study, in which researchers take a group of people who have developed cancer and determine how they’re different from healthy people. They might, for example, observe high rates of lung cancer in a group of construction workers, and link it back to asbestos exposure in their work environments. Some doctors conduct correlational studies, which compare groups of people on a population-wide basis rather than examining the behavior of specific individuals. Chinese physicians used this strategy to find that esophageal cancer was abnormally common in areas where residents eat lots of fermented pickles.

One problem with these methods is that it’s difficult to prove whether the association is causation or mere correlation: High rates of pickle consumption and the development of esophageal cancer could be a mere coincidence, or both pickle eating and esophageal cancer could each be the result of something such as a lack of vegetables. And, in the case of VOCs, people aren’t always able to reliably quantify their levels of exposure to a chemical.

The International Agency for Research on Cancer classifies chemicals as carcinogenic, probably carcinogenic or possibly carcinogenic. VOCs appear in all three categories.

Benzene, which has lots of uses including dry cleaning and the making of plastic, is a well-studied, proven carcinogen. It’s bad enough that the Environmental Protection Agency doesn’t tolerate anything above a minuscule amount in public drinking water and has developed good data on the degree to which it raises a person’s cancer risk.

By contrast, chloroform, which is released during chlorination of swimming pools and at paper mills, is only possibly carcinogenic. While inhalation of very high levels is immediately dangerous, no one really knows how much is safe over the long term. (There’s little reason to believe that summer swimming season is going to give your child cancer, in case you’re wondering, although there have been a few studies suggesting prolonged exposure could lead to asthmalike symptoms.) Other VOCs are completely unstudied.

What this means for the average consumer is that more research is needed. When a paint manufacturer or maker of some other “VOC-free” product warns you about VOCs in a rival’s goods, you should ask which VOCs they’re talking about, what makes them think they’re dangerous and how they know the potential exposure levels are dangerous. If you’re really ambitious, you can review IARC monographs, and even the underlying studies, which are often publicly available. Unfortunately, until we develop convenient, reliable testing mechanism, this is all a lot of educated guesswork.