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Dr. Sal Iaquinta Robert Tong

Over the past decade there has plenty of discussion about leaf blowers. Many California cities have bans or partial bans on leaf blowers and some Marin cities are considering their own restrictive legislation.

The Internet is littered with blogs castigating leaf blowers, leaving you with Zagat-review-sized snippets that make it sound like the creator of the leaf blower was out to destroy humankind and the world with it. Get your "eardrums blown out" while breathing "toxic exhaust fumes" and inhaling "flying spores." And when I read words like "greatest threat," I start to think the whole thing might be a bunch of hot air. So I decided to spend a few minutes to sift out the science from the hyperbole.

There are a number of arguments against leaf blowers, including  human health  (IJ photo/Frankie Frost)

There are a number of arguments against leaf blower. Although eroding soil, damaging plants, and spreading weed seeds are legitimate concerns, I focused more on the effects on human health.

First, is noise pollution. Sure, they are annoying, but they actually can cause hearing damage to the frequent user. The city of Davis has limited the noise level of leaf blowers to 70 decibels at a distance of 50 feet. That helps the bystanders, but that still means the user should be using high-quality ear protection. Other cities have restricted leaf blower use to certain hours of the day. Noise alone was a reason for Beverly Hills to ban leaf blowers back in 1978. Perhaps it is proof that movie stars prefer the sound of their own voice over ... everything.

A quieter motor doesn't sidestep the second issue — air pollution. A number of cities have restrictions on gasoline motored leaf blowers because they are considerable polluters for their small size. But gas leaf blowers are only one type of small motor, any city concerned about them should look at all the other devices that use them. Unfortunately, our EPA has yet to create any emissions standards for these machines.

Battery-powered blowers tend to be quieter and don't create dirty exhaust. A number of cities, including Los Angeles, restrict blowers to battery only.

The bigger pollution problem is the particulate matter these blowers kick up. There have been a few studies addressing this issue. In the 1990s a study out of UC Riverside examined how much particulate matter got kicked up on lawns or parking lots when using leaf blowers or blower vacs versus using rakes and brooms. As expected, blowers and vacs put far more particulate matter in the air than raking. There was one surprise— brooms on concrete dirtied the air far more than brooms on asphalt.

The American Thoracic Society published a review regarding the health effects of outdoor pollution. Its finding is fascinating but probably not shocking. Researchers found cardiovascular mortality, hospital admissions for respiratory problems and emergency room visits for asthma were directly related to the level of particulate matter in the air across a number of cites over decades. The study did not specifically address leaf blowers, but putting the two studies together makes a strong case for using a rake.

Along the same lines, the jet of air also puts dust and pollen in the air. There are no studies specifically looking at leaf blowers and allergies, but it makes sense that these devices would definitely increase the allergic triggers for anyone nearby. Also unstudied is how long it takes the additional airborne particulate matter to settle back to baseline.

The health concerns regarding these devices are legitimate. In a world where we constantly replace physical labor with machinery, maybe raking the lawn for a little while can be a form of exercise while keeping the ground where it belongs — out of our lungs.
