Leaf blower pollution

Imagine 300 Ford F-150 Raptors circling around your house. Now imagine one gardener using a gas leaf blower. Guess which releases more of the hydrocarbon pollution?

It may be the leaf blower! In a 2011 laboratory test, the two-stroke blower emitted nearly 300 times as much non-methane hydrocarbon per minute as an F-150 truck.

Small two-stroke leaf-blower engines can emit large amounts of unburned hydrocarbons and carbon monoxide, while resuspending dust into the air.

This rabbit hole began with welcome local news. On August 24, Charlottesville announced that the Downtown Mall custodial crew now uses electric leaf blowers exclusively. Staff report comparable power and performance, much less noise, and almost no remaining blower-noise complaints.

The comparison#

In that test, Edmunds compared a 50.8 cc two-stroke Echo backpack blower and a four-stroke Ryobi blower with a 2011 Ford F-150 Raptor. The blowers followed an adapted version of the same 31-minute federal driving cycle. Emissions are weighted grams per minute:

The two-stroke blower emitted nearly 300 times as much non-methane hydrocarbon and 23 times as much carbon monoxide per minute as the truck. Edmunds calculated that about 30 minutes with that blower produced as much hydrocarbon pollution as driving the Raptor 3,887 miles.

This is one test of specific machines, not a universal conversion between leaf blowing and driving. It compares particular pollutants, not total environmental harm: the Raptor emitted more carbon dioxide, while the blowers were dramatically worse for local hydrocarbon and carbon-monoxide pollution.

Why the two-stroke engine is so dirty#

A California Air Resources Board report explains:

Typical two-stroke designs feed more of the fuel/oil mixture than is necessary into the combustion chamber. Through a process known as scavenging, the incoming fuel enters the combustion chamber as the exhaust is leaving. This timing overlap of intake and exhaust port opening can result in as much as 30% of the fuel/oil mixture being exhausted unburned. Thus, exhaust emissions consist of both unburned fuel and products of incomplete combustion.

The blower adds a separate problem: high-velocity air lifts dust from the ground. CARB found the amount difficult to measure reliably, so estimates of this resuspended particulate pollution should be treated cautiously.

It may not just be the leaf blowers#

Leaf blowers belong to the broader category of small off-road engines, along with lawn mowers, chainsaws, pressure washers, air compressors, and portable generators. In its 2021 rulemaking baseline, CARB estimated that this category emitted more nitrogen oxides and reactive organic gases in California than light-duty passenger cars. Without further regulation, it projected the category would emit 1.8 times as much of those pollutants as passenger cars in summer 2031. That comparison covers the entire category, not leaf blowers alone.

Towards lower pollution in general, especially for children#

Children are not small adults. A Paris-region health assessment notes that they breathe more air relative to their body weight and that their lungs are still developing, making avoidable air pollution especially consequential.

The policy evidence makes that risk concrete. A London’s natural experiment followed 3,414 primary-school children during the first four years of the Ultra Low Emission Zone (ULEZ). As residential nitrogen-dioxide exposure fell faster in London than in Luton, children’s lung-function growth was also faster; the share with impaired lung function fell from 14% to 9% in London, compared with 9% to 7% in Luton. The study cannot isolate the ULEZ from every concurrent change, but it connects cleaner neighborhood air with children’s developing lungs.

If we remove dirty vehicle exhaust around schools, people, especially children, become much healthier. Why do we still run these highly polluting engines for purely cosmetic yard cleanup, especially when electric alternatives exist?

What the city can do#

The Downtown Mall transition shows that electric blowers can handle demanding daily municipal work. Now Charlottesville can make that success the default:

• publish an inventory and phase-out schedule for the city’s remaining gas-powered lawn equipment;
• make electric equipment the default for new city purchases and landscaping contracts, with narrow documented exceptions;
• prioritize schools, parks, sidewalks, and dense residential areas, where people are close to the exhaust;
• help small landscaping businesses switch through rebates, grants, or shared charging infrastructure.

What we can do#

• Leave leaves where practical; otherwise, rake or use electric.
• Ask hired landscapers to use electric equipment.
• Thank the city for making the Downtown Mall quieter and cleaner.
• Ask the Office of Sustainability and City Council for a timeline to extend the transition across city operations and contracts.

Sources#

• Electric Leaf Blowers Bring Cleaner, Quieter Maintenance to Downtown Charlottesville, City of Charlottesville
• Emissions Test: Car vs. Truck vs. Leaf Blower, Edmunds
• 2021 Small Off-Road Engine Rulemaking Staff Report, California Air Resources Board
• A Report to the California Legislature on the Potential Health and Environmental Impacts of Leaf Blowers, California Air Resources Board
• London’s Ultra Low Emission Zone and children’s lung-function growth, CHILL study
• Air quality around Parisian schools, Airparif
• Expected health benefits for children from a Paris-region low-emission zone, Santé publique France