The pesticides you use on your lawn to get rid of weeds and insects are part of a $10 billion-a-year industry. But some doctors are becoming more concerned about your exposure to those chemicals, CBS News correspondent Vinita Nair reports.

Joe Holland has been in the lawn care business for 30 years. His work requires him to be around a variety of chemicals, which is why he always tells his workers to take precautions.

"You always have to protect yourself when you're using any chemicals, no matter the grade," Holland said. "You have to wear a long sleeve shirt, long pants."

The chemicals his workers are using are known as herbicides and insecticides, designed to kill invasive plants and ward off bugs like mosquitoes. The most common chemicals used are glyphosate 2, 4-D, and permethrin.

Dr. Phil Landrigan, professor of pediatrics at New York's Mount Sinai Hospital, studies the effects of these chemicals on humans, in particular children and pregnant women.

"I think the fact that they have been around for a long time engenders a false sense of security," Landrigan said.

This week, he presented his findings at a congressional briefing on the health risks of overexposure.

"There is also concern that pesticides of all kinds can damage the developing nervous system and can result in learning disabilities in children, behavioral problems and possibly chronic diseases like Parkinson's," Landrigan said.

The doctor insists that some pesticides can stay in your system for years.

"Older pesticides like DDT can stay in the human body for years, even decades," Landrigan said.

But Dr. Josh Bloom of the American Council of Science and Health says these chemicals have been used in the U.S. for at least 60 years and pose no risk.

"There are so many hundreds of things more dangerous in everyday life than this that it is not even worth thinking about," Bloom said.

New York is one of many states that requires landscapers to put down flags, warning residents that a lawn has been freshly treated.

Joe Holland says his landscaping clients regularly ask about the chemicals he's using.

"The questions I get the most are 'when can my kids and my dog go out on the lawn' and my answer is usually 24 hours," Holland said. "If it doesn't get watered for two days, we recommend you don't go out there for two days."

There is no scientific standard about how long to stay off the lawn after it's treated. Landrigan wants to see that change. Joe Holland says he and his workers mark each lawn with flags and instruct homeowners when it's safe to venture out into their yards.