In phone call after phone call, Rick Stewart has been explaining to long-time customers what types of chemicals his company, Stewart Pest Control, uses on their properties.

Pesticides are on everyone's mind after officials announced that two young sisters in Layton, Rebecca, 4, and Rachel Toone, 1, likely died after inhaling gases from a chemical used by another pest-control company to kill voles.

"As long as we've been in business and longer, there has never been an incident even close to this in Utah," Stewart said. "We're getting a lot of questions from our customers. We actually don't even do that kind of treatment."

Utahns are calling experts anxious to know if the products they use — or hire others to apply — are dangerous. And the short, too-simple answer is yes, said Diane Alston, entomologist with Utah State University Extension. Anything, she said, has the potential to do harm if it's not used right. And pesticides can be very dangerous. "I don't think most people realize the importance or potential consequences." Even so, "Given all the products, the incidents (of harm) we know about are pretty low."

Pesticides come with various degrees of danger and levels of precaution. So Utah's Department of Agriculture and Food, which oversees local use of pesticides, holds special workshops every year to teach professionals and do-it-yourselfers how to handle them. Clark Burgess, who heads the pesticide program, said 10,500 pesticides are registered in Utah. Of those, about 250 are "restricted" by the Environmental Protection Agency — they can only be sold by one of 117 specially-licensed restricted-use dealers, and those dealers can only sell to specially licensed applicators.

Anything a consumer could buy is "general use."

Utah has registered 843 companies and 1,800 individuals who apply pesticides. Each took the training course, passed the test and must recertify every three years.

And that's where Burgess tells wary consumers to begin. Ask to see the license; each worker is required to have it on the job. Also ask to see the label of any substance the worker will apply. Look at that for "signal words." "Caution" is the least hazardous, Burgess said, while "Warning" falls in the middle. "Danger" and "Danger-Poison" mean high risk.

Reading the label is the best safety precaution, Alston said, but people rarely do because labels "tend to be long with legalese-type language that can be difficult and boring. So people tend to skim or skip."

The label is a legal document that spells out how to use potentially dangerous products. And even a homeowner who hires out the job should read it because it contains important information, including how long a product will take to dry, whether to remove pets, how close to homes a product can be used and possible symptoms of exposure. Labels also tell what protective clothing is required and more. Customers also can look at a product's Material Safety Data Sheet, available online. And Agriculture has a free pesticide safety manual, available at locations throughout the state.

Stewart said his commercial customers frequently ask questions about the chemicals and want him to use the least-toxic products available. And most pest-control problems can be solved with products in the caution range.

But restricted-use products, while the most dangerous, are not the only ones that can cause either chronic or acute harm. A homeowner who uses a widely available, popular product without paying attention to the directions and warnings can cause injury to himself or others.

Last year, for the first time, pesticide exposure made it to the Utah Poison Control Center's list of the top 10 reasons people called, spokeswoman Marty Malhiero said. "The majority, 95 percent, were unintentional exposures — inhalation, some skin and eye exposures. We caution people about drinking (pesticides). We see problems in the garage, where you have diluted a pesticide or herbicide to use it and then store it in a sports drink bottle or something, without a label."

Alston most often hears of cases where small children got into concentrated product. And the harm done, she said, often hinges on the size of the person and the dose. Small children may be at higher risk not only for size, but because they are growing and metabolize things faster. The need to store pesticides properly is critical.

The experts at Poison Control tell people to buy the smallest amount necessary of any potentially toxic substance like pesticide and dispose of any leftovers appropriately. When possible, Malhiero added, use nonchemical methods and prevention. She suggests you remove water, store food in sealed containers, block hiding places, caulk cracks and remove piles of wood and diseased plants. Then choose the form of pesticide best targeted for what you want.

Most pesticide poisonings are "slow and insidious," she said. It's easier to spot an acute exposure than one that builds up from repeated use of a product. But symptoms tend to be nonspecific: vomiting, sweating, nausea, dizziness, headaches, confusion, weakness, chest pains, body aches, muscle cramps and breathing difficulty. It's easier to spot contact effects, such as itching, rash, blisters or burns. Permanent respiratory damage occurs less often. Some exposures are believed linked to long-term health problems including cancer. Pesticides damage people and animals through four main exposure routes: skin, eyes, mouth and inhalation.

Pesticides might not be suspected "unless someone is really overdoing it." It can look like flu, heat exhaustion, asthma, respiratory or intestinal infections, even a hangover.

If you suspect exposure, provide the label when you seek medical care, if possible.

Missy Henriksen is vice president of public affairs for the National Pest Management Association, but she's also a homeowners and consumer. And with any service that walks through her door, she said she wants to know first about licensing and then about membership in national associations. That, she said, "shows a commitment to the industry. Associations are noted for providing ongoing training." She also gets recommendations from family and friends who were happy with a service. With pest control specifically, she said, she wants someone who is "quality-pro certified," which means they've met certain standards and had background checks.

Finally, experts note there are different treatments for every pest problem. If one worries you, talk about options.