Old paint on the exterior of your home can be just as much a risk as old paint on the inside, if not more so. That's because lead concentrations can be higher in exterior paints. High lead levels are known to cause serious developmental delays in children and have been linked to seizures and high blood pressure in adults.

The trouble with lead dust outdoors is that once it gets in your soil, it will be there forever. "Lead does not biodegrade, or disappear over time, but remains in soils for thousands of years," according to the Penn State Extension. Children playing around the house can be exposed to it, and lead dust can be tracked inside. So your best bet is to prevent it from getting into the soil in the first place by following lead-safe practices.

Painting the exterior of your home is a challenging DIY job to begin with. Add in the complexities of dealing with lead-based paint on a house built before 1978, and you’re better off hiring a pro certified by the Environmental Protection Agency, as required by a 2008 law. Ask prospective contractors for their certification, and then take the following three steps to make sure they're following lead-safe practices.

Watch Out for White

If your house was built before 1978, assume it's among the millions of houses that have at least one coat of lead-based paint; 83 to 86 percent do, according to the Centers for Disease Control and Prevention. The CDC also points out that older houses generally contain more coatings of lead paint, and older paints often have higher concentrations of lead.

For example, before 1955, white exterior paint was frequently made from a 50/50 mixture of linseed oil and lead, resulting in a lead concentration as much as 50 times higher than what was in other lead-based paints. So if your older home was painted in a shade of white, exercise extreme caution and care.

You can do your own lead test with a kit from a home center. But if you're hiring an experienced EPA-licensed painter, let the pro do the testing before the paint job begins. A high-lead finding might even steer you away from painting and toward siding that safely covers contaminated paint.

Take Extra Care Around Trim

Lead concentrations tend to track pretty closely to the level of gloss in the paint. That's why the EPA reports that lead is more common in areas painted with glossy paint, such as trim, windowsills, and doorframes. Because windows and doorways get heavy use, paint in those areas is usually in the worst condition, requiring the most scraping and sanding.

Trim and doorways are often left uncovered even if you have siding installed. So don’t let a painting pro skip taking precautions when painting the trim. To capture lead dust before it contaminates the soil, the area should be contained with plastic sheeting that extends at least 10 feet beyond the work area. Tightly shut any doors and windows within 20 feet, wear shoe covers to prevent tracking paint dust into the house, and avoid painting on windy days so the dust doesn't blow around.

Let nearby neighbors know there's work going on so they can keep their windows and doors closed as well.

Minimize Dust and Fumes

Undisturbed lead paint that’s in good condition doesn’t pose much of a risk on its own, particularly if additional top coats of lead-free paint are holding it in place. But part of any good paint job includes removing cracked or peeling paint, either by scraping it with a knife, sanding it, or removing it with a heat gun. That ensures a smooth finish and allows the new coat to adhere better.

But sanding and heat blasting should be a last resort, because doing so can produce dust and fumes that can travel and settle into your soil or get kicked up by the wind. If your painter needs to remove layers of paint this way, the sander must be connected to a HEPA vacuum while he works, and he’ll need to set up a barrier of plastic sheeting if the work is less than 20 feet from your property line to protect your neighbor's soil as well.