Every city in america is watching dallas tonight, and this is the question. Can human ingene knewty outflank all those mosquitos carrying the west nile virus? Dallas is the epicenter of the deadly... See More
Every city in america is watching dallas tonight, and this is the question. Can human ingene knewty outflank all those mosquitos carrying the west nile virus? Dallas is the epicenter of the deadly outbreak, and tonight, planes will spray for chemicals on backyards, playgrounds, churches, as more than 2 million people move inside to wait and see if this works. Abc's ryan owen is in dallas for us tonight. Reporter: Crews spent the day after hosing down playground equipment and wiping off drinking fountains. After a night of pesticides raining down on dallas, there's no such thing as too careful. Last night, those planes flew low over some of big d's biggest neighborhoods. Residents warned to stay inside. This is by far the most difficult call I've had to make as an elected official. Reporter: Dallas county judge clay jenkins reluctantly pulled the trigger on the air assault after ten people here died of west nile virus. He says without immediate action, the death toll would grow. There were no scientists saying don't do it. Reporter: What's falling from the sky is the same pesticide ground crews have been spraying here for weeks. Aerial spraying actually requires fewer chemicals, just two tablespoons can treat a football field. The epa says the chemical mist is only harmful to people or pets if it's swallowed, but some doctors say people with asthma or respiratory problems are at risk. The pesticide called duet is toxic to bees and fish. Which is why there was a scramble to cover ponds, and why this family blanketed their backyard. We also have two dogs and a cat, so, we just went ahead and covered their part of the yard too, as well as the area my daughter plays in, just to be extra safe. Reporter: While those planes unnerved a lot of people, this woman says she was relieved to hear them buzz by. We've had deaths. It's better to have poison falling from the sky than to have people die. Reporter: More spraying on tap tonight foras like this one. Other cities that have used aerial spraying say they killed 80% to 90% of the mosquitos. It will be a few days before we know how well it works in dallas. But other cities with smaller west nile outbreaks will be watching.
This transcript has been automatically generated and may not be 100% accurate.