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New California rules aimed at curbing the surprising amount of pollution coming from leaf blowers, lawn mowers and other small gas-powered machines cleared a final hurdle Monday, and are set to take effect on Jan. 1.

The requirements mark another step in the state’s long-running battle to reduce emissions from a category of small engines that have come to rival cars as a source of smog-forming pollution.

As FairWarning reported in September, while automobile motors have been overhauled over the decades to slash emissions, there has been no equivalent clean-up of small off-road engines, a category including lawn and garden equipment and generators. As a result, those gas-powered machines are on their way to becoming the worse polluters. For example, the California Air Resources Board says the smog-forming contamination from running a top-selling leaf blower just one hour matches the emissions from driving a 2016 Toyota Camry for 1,100 miles.

In the Los Angeles area as soon as 2020, the small machine category is expected to overtake ordinary sedans as a source of oxides of nitrogen and reactive organic gases, which are precursors to smog. Nationwide, the Environmental Protection Agency estimates that small nonroad engines already account for 81 percent as much of those pollutants as sedans, a comparison that excludes SUVs and light trucks.

Noisy, But That’s Not All

The pollution consists of both combustion exhaust when the machines are running and evaporative emissions – the fumes seeping from gas tanks and fuel lines even when a machine is idle. The regulatory changes taking effect in January apply only to evaporative emissions, which account for 41.3 tons a day of pollution in California, or 35 percent of the total air contamination from the small machines.

Air board officials, however, plan to propose another batch of rules in 2020 to further curb both evaporative and exhaust emissions. That move is intended to accelerate a shift in the marketplace from gas-powered equipment to so-called zero emissions electric machines. “In the longer term, what we need to do is transition entirely away from gasoline-powered off-road engines,” said Bill Magavern, policy director for the California advocacy group Coalition for Clean Air.

The goal is to curb pollution linked to lung cancer, heart disease, strokes, asthma and other respiratory ailments. Those thought to be most at risk are landscaping workers who spend long hours operating gas-powered equipment, and who may be exposed to elevated levels of ultrafine particles that pose a breathing hazard. Air tests commissioned by FairWarning in June and July found high ultrafine particle concentrations around operating machines – in one case, the concentration was more than 50 times higher than at a nearby traffic-clogged intersection.

An air pollution specialist with the Air Resources Board, Christopher Dilbeck, said another concern stems from the fact that lawn and garden equipment often is stored in an attached garage. As evaporative emissions escape from those machines, he said, “You could have vapors intruding into that house,” posing a health risk to an entire family. With the new evaporative emissions rules, Dilbeck said he hopes “we will be able to prevent things like that.”

A California regulation adopted in 2003 was supposed to substantially curb evaporative emissions, but spot checks conducted from 2008 through 2015 on 60 machines showed that 33, or more than half, failed to meet state air quality standards. That spurred the air board last November to unanimously approve tougher testing and enforcement rules. One of the key changes was aimed at generators, riding lawn mowers and other non-handheld machines.

Until now, under a concession made to the power equipment industry, air board officials focused only on emissions from certain engine components of these machines – not on the overall emissions from the entire piece of equipment. So if heavy emissions escaped from, for example, the carburetor – a component that has escaped enforcement scrutiny – the agency’s hands were tied. With the new rules, the agency theoretically can crack down.

The new rules made it through a final hoop on Monday when they were cleared by the California Office of Administrative Law, which reviews state regulations before they can take effect.

The Outdoor Power Equipment Institute, which has led industry opposition to the new rules, declined to comment for this story. In a June letter to California officials, the industry group accused the air board of a “failure to address the true costs” of the tougher rules. It also asserted that the flaw “will result in the rule being invalidated” by the Office of Administrative Law – a prediction that was proved wrong Monday — “or possibly by a court,” suggesting that the industry was prepared to sue California to block the changes.

Air board officials say the new rules will lead to average retail price increases of up to $2.72 per item. That would equate to a 3.9 percent increase for a $70 low-end string trimmer to a 0.05 percent increase for a $5,000 riding mower.

While California often is a trend-setter in environmental regulation, other states won’t be following its lead this time. After California expanded its regulations in 2003, industry officials went to Congress to try to block the state’s authority to impose tougher-than-federal standards for small off-road engines. California managed to keep its authority to set such standards but, under a legislative compromise, other states were barred from doing the same.

About FairWarning

This story was reported by FairWarning (, a nonprofit news organization based in Pasadena, Calif., that focuses on public health, safety and environmental issues.