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Particulate Matter Emissions from Leaf Blowers1
Alexander D. Blumenstiel, Ph.D.
(Version 2)
May 22, 2015
1. Introduction
Leaf blower operators and others inhale fine particles in the fugitive dust emissions
blown into the air from the surfaces they clear.2 The referenced epidemiological studies
strongly suggest that such particles, especially particulate matter (PM) under 2.5
micrometers and between 2.5 and 10 micrometers in diameter, contribute significantly
to the incidence of and mortality from a variety of respiratory, cardiovascular,
cerebrovascular and other diseases. The following sections review and extrapolate
findings reported in "Particulate Matter Emissions Factors and Emissions Inventory from
Leaf Blowers in Use in the San Joaquin Valley”3 (referred to herein as ‘the San Joaquin
study’) to estimate average annual exposures of leaf blower operators and others to
these emissions.
Since its 2006 publication, the San Joaquin study has not been independently
replicated. Nor has it been extended to measure leaf blower PM emissions from a full
spectrum of common leaf blower applications nationwide. And, although its findings can
be mathematically extrapolated, it did not empirically measure collective emissions from
multiple leaf blowers operating in close proximity.
The San Joaquin study measured the dispersion of suspended particles in two enclosed
test chambers. “Seventy-two runs were performed using surrogate material on asphalt
and concrete surfaces using the 20m long chamber.” This chamber, at the UCR CECERT (Center for Environmental Research and Technology) facility in Riverside, was
2m wide, 2m high and 20m long.4 A second enclosed chamber, 2m wide, 2m high and
10m long was used to perform tests at additional locations.5 Emissions detectors
1
Copyright © 2015 by Alexander D. Blumenstiel. All rights reserved. Except as otherwise noted, the analysis and
conclusions herein are solely the author’s.
2 "FUGITIVE EMISSIONS means those emissions which could not reasonably pass through a stack, chimney, vent,
or other functionally equivalent opening." Massachusetts 310 CMR: DEPARTMENT OF ENVIRONMENTAL
PROTECTION, 310 CMR 7.00: AIR POLLUTION CONTROL; 21.
"Fugitive dust emissions impact a varying number of people, depending on one's proximity to the source, the size of
the particles, and the amount of time since the source resuspended the particles.". "The particulate matter (PM)
swept into the air by blowing leaves is composed of dust, fecal matter, pesticides, fungi, chemicals, fertilizers, spores,
and street dirt which consists of lead and organic and elemental carbon." A Report to the California Legislature on
the Potential Health and Environmental Impacts of Leaf Blowers, California Environmental Protection Agency Air
Resources Board Mobile Source Control Division, February 2000
(http://www.nonoise.org/resource/leafblowers/carbleafblower2000.pdf); 2; 8.
3 Particulate Matter Emissions Factors and Emissions Inventory from Leaf Blowers in Use in the San Joaquin Valley:
Final Report. Prepared for San Joaquin Valley Unified Air Pollution Control District, Dennis R. Fritz, et al., College of
Engineering, Center for Environmental Research and Technology, University of California, Riverside, January 27,
2006 (https://www.valleyair.org/newsed/LeafBlowers/LeafBlower.pdf)
4
Ibid. 18
5
Ibid. 24.
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measured particulate matter concentrations in the test chambers while and after the leaf
blower’s and other tools were operating.
The principal purpose of the study was to ”develop emission inventories for counties in
the San Joaquin Valley”.6 It was not to determine the exposure of operators and
proximate others to concentrations of fine particulate matter in fugitive dust emissions
from leaf blowers while they are running.
2. Particulate Matter Emissions from Leaf Blowers
The following Table from the San Joaquin report7,”summarizes the results in general
categories”.8 It shows the average quantity of Total Suspended Particulates (TSP),
PM2.5 and PM10 emitted by leaf blowers, a push broom and a rake clearing debris from
one square meter of concrete or asphalt surfaces, lawns, gutters, and from packed dirt
or from clearing cut grass from walkways. Since “the (PM in the test) chamber was not
well mixed for several minutes,” these results were “calculated by multiplying the
concentration once it stabilized (when it became uniformly mixed) by the volume of the
enclosure and dividing by the area treated.” 9 Therefore, in accord with the principal
object of the San Joaquin study as previously noted, Table 1 neither reports nor
represents the concentrations of airborne particulate matter in emissions to which
operators and proximate others are exposed while leaf blowers and the other types of
tools tested are in operation.
Table 1. Summary of Emissions Factors
6
Ibid. 4.
7
Ibid; 2.
8
Ibid; 2
9 Determination Particulate Emission Rates from Leaf Blowers, Dennis Fitz, et.al, , College of Engineering-Center for
Environmental Research and Technology University of California, Riverside, CA , and San Joaquin Valley Unified Air
Pollution Control District (http://www.epa.gov/ttnchie1/conference/ei15/session5/fitz.pdf); 7
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2.1. Total Suspended Particulates (TSP)
Table 1 indicates that, after the leaf blowers and other tools ceased operating, and their
particulate matter emissions were “uniformly mixed” in the volume of air enclosed in the
test tent structures employed for the trials in this study, the results were that:
 “There was little difference between blowing and vacuuming with the model that
was tested.
 Sweeping with a broom on concrete created significant PM emissions whereas
sweeping asphalt did not.
 Raking leaves did not generate significant amounts of PM.10
The average dispersed total suspended particulates (TSP) found in this study “in terms
of milligrams per meter squared” (mg/m2) cleaned” 11 in the six types of leaf blower trials
was:
(100+ 80+3+50+160+9) ÷ 6 = 68.7mg/m2
2.2. PM10
Of the average 68mg/m2 of TSP dispersed after the leaf blowers ceased operating in the
six types of trials, the average PM10 emissions was:
(80+60+2+30+120+6) ÷ 6 = 49.7mg/m2
PM10 emissions constituted 72% of the dispersed TSP from the leaf blower trials in this
study.12
A homeowner using a leaf blower 1/2 hours per week 26 weeks per year (and others in
the immediate vicinity) would on average be exposed to 49.7 milligrams per cubic meter
(µg/m3) of airborne PM10 per square meter cleared for 13 hours per year. A
commercial lawn/garden maintenance contract worker using a leaf blower for 10
minutes ten times per day13 5 days per week for 26 weeks per year would on average be
exposed to inhaling this amount of fine PM 217 hours per year.
2.3. PM2.5
Of the average 68mg/m2 of TSP dispersed after the leaf blowers ceased operating in the
six types of trials, the average PM2.5 emissions was:
(30+20+1+9+80+2) ÷ 6 = 23.7mg/m2
PM10 emissions constituted 35% of the dispersed TSP from the leaf blower trials in this
study.
10
Particulate Matter Emissions Factors and Emissions Inventory from Leaf Blowers in Use in the San Joaquin Valley:
Final Report.; 2.
11
Ibid.
12
PM10 emissions include PM2.5 emissions.
13
Echo, Incorporated, “Leaf Blower Noise” (http://www.leafblowernoise.com)
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3
Operators’ and Proximate Others’ Exposure
The TSP, PM10 and PM2.5 averages in Table 1 do not, however, account for the
exposure of operators and proximate others to particulate matter emissions while the
leaf blowers are operating.
This assumes a constant rate of leaf blower fine PM emissions, as in the San Joaquin
study. For example, a leaf blower directed at a concrete surface covered with the
materials used in that study will continuously emit 30mg. of PM2.5 and 80mg. of PM10
per square meter (including 50mg. of particles between PM2.5 and PM10). It assumes
that the quantity of fine particulate matter cleared from a one square meter surface is
the same quantity of fine PM airborne in one-cubic meter (m3), as in the San Joaquin
study, which measured the airborne mass of emitted fine PM at heights of 0.5m, 1.0m
and 2.0m.14
The San Joaquin study found that the fine PM blown into the air by leaf blowers from
the surfaces in the experiment rapidly dispersed. Therefore, this estimate assumes
those proximate to leaf blower operations are exposed on average to a constant total of
49.7mg per cubic meter of PM2.5 and PM10, though the amount of hazardous PM10
they inhale and retain in their respiratory, cardiovascular and cerebrovascular systems
is likely cumulative.15
3. OSHA Permissible Exposure Limit (PEL) Compliance
The report cites U.S. Department of Labor Occupational Safety and Health
Administration (OSHA) and California Occupational Safety and Health Administration
(CalOSHA) permissible exposure levels for PM up to 10 micrometers. "The OSHA
permissible exposure level (PEL) (level that a healthy individual can work in for eight
hours) is 10mg/m3 and the CalOSHA level short-term exposure level (STEL) (level that
a healthy individual can work in for fifteen minutes) is 20mg/m 3."16
Assuming their continuous exposure to 49.7mg of airborne PM10, including 23.7mg per
cubic meter of airborne PM2.5 when clearing surfaces:
Private operators’ average PM10 exposure from leaf blowers exceeds the 20mg/m3 STEL by
29.7mg/m3 and PM2.5 exposure by 3.7mg/m3 for 13 hours per year.
Commercial operators' average PM10 exposure from leaf blowers exceeds the 20mg/m3 STEL
by 29.7mg/m3 and PM2.5 exposure by 3.7mg/m3 for 10 minutes ten times per day, or 217
hours per year.
Alternatively, based on the following U.S Department of Labor OSHA milligrams per
cubic meter dust PELs, the average respirable mineral dust particle PEL is
14
The PM2.5, PM10 and Total Suspended Particulate (TSP) emissions factors in the table. Ibid; 23.
15 “The air-jet generated by blowers with velocities of 185 miles per hour or more spreads dust, dirt, pollens, animal
droppings, herbicides and pesticides into the air. The effect lasts for hours on particulate matter that is 10 microns in
diameter or smaller. The ARB has estimated that each leaf blower entrains (puts into the atmosphere) 5 pounds of
particulate matter per about half of which is 10 microns or smaller.” Leaf Blower Pollution Hazards in Orange County,
Orange County Grand Jury, April 1999; (http://www.ocgrandjury.org/pdfs/leafblow.pdf)
16 “Ibid;17.
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(10+2.4+10)/3 = 7.5mg/m3, and average total mineral dust PEL is (30+80+2.4+10+15)/5
= 27.5mg/m3.17
• At an average of 49.7 mg/m3, the fine PM emissions from leaf blowers exceed
the OSHA respirable mineral dust PEL by 49.7 - 7.5 = 42.2 mg/m3 and the OSHA
total mineral dust PEL by 49.7 - 27.5 = 22.2mg/m3.
• At an average of 23.7mg/m3, the fine PM2.5 emissions from leaf blowers exceed
the OSHA total respirable mineral dust PEL by 23.7 - 7.5 = 16.2 mg/m3.
Leaf blowers emit these and other types of particles. Both totals include respirable coal dust. “Occupational Safety
and Health Standards, Toxic and Hazardous Substances, 1900.1000, Table Z-3, Mineral Dusts”, United States
Department of Labor, Occupational Safety and Health Administration, [58 FR 35340, June 30, 1993; 58 FR 40191,
July 27, 1993, as amended at 61 FR 56831, Nov. 4, 1996; 62 FR 1600, Jan. 10, 1997; 62 FR 42018, Aug. 4,1997]
(https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9994)
17
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4. Annual Fine PM and Exhaust Emissions from Leaf Blowers - Preliminary
Estimate
Although leaf blowers have been sold in the United States since 1977, the author has
found neither comprehensive sales nor lifecycle data from which to directly calculate the
number of leaf blowers in operation nationally, regionally or by state and municipality in
order to directly determine the current total U.S. leaf blower PM10 emissions. The
following estimates of the number of leaf blowers in use and the current total annual
PM10 emissions from those leaf blowers are extrapolated from secondary information in
the referenced sources.
With three-million estimated average annual sales, assuming 50% annual obsolescence
after the first year, the estimated total number of operational leaf blowers in the U.S.
today is: 37 years x 3,000,000 = 111,000,000/2 = 55,000,000 leaf blowers currently
operational in the United States. Just for the estimated 217 hrs./year per leaf blower of
commercial operation, this comes to 11,935,000,000 total estimated hours of leaf
blower operation per year.
Assuming half of the leaf blowers are two-cycle and half four-cycle (which likely not
accurate, , since the vast majority are likely two-cycle), according to the cited Edmunds
study, the average leaf blower emits (3.714+6.445)/2 = 5.0795 weighted grams per
minute of CO, which is 18.4 times more than a 2011 Ford Raptor’s 0.276 weighted CO
grams per minute.
The estimated 55,000,000 leaf blowers therefore produce 279,372,500 C0 grams per
minute, or the C0 equivalent of 1,012,000,000 Ford Raptors.
At the estimated 217 annual hours of operation each, the 55,000,000 leaf blowers
produce (279,372,500 x (60 x 217)) = 3,637,429,950,000 weighted grams, or 3,637,429
metric tons of CO per year.
2.4. 4.2 4.5 Net Operational Total (pending estimation)
2.5. 4.6 Fourteen Year Operational Variance (pending estimation)
2.6. 4.7 Total Leaf Blower Fine PM Emissions at 5 lb../hr
According to the Santa Ana County Grand Jury’s April 1999 report:
As previously noted, “The air-jet generated by blowers with velocities of 185 miles per
hour or more spreads dust, dirt, pollens, animal droppings, herbicides and pesticides
into the air. The effect lasts for hours on particulate matter that is 10 microns in diameter
or smaller. The ARB (California Air Resources Board) has estimated that each leaf
blower entrains (puts into the atmosphere) 5 pounds of particulate matter per hour
about half of which is 10 microns or smaller.”18
•
100 hrs (pending)
•
217 hrs. (pending)
•
15 hrs. (pending)
18
Leaf Blower Pollution Hazards in Orange County, Orange County Grand Jury, April 1999; page 4
(http://www.ocgrandjury.org/pdfs/leafblow.pdf)
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2.7. 4.8 Total Personal Use Annual Fine PM Emissions (pending estimation)
2.8. 4.9 Total Contractor Annual Fine PM Emissions (pending estimation)
2.9. 4.10 Net Total Annual Leaf Blower Fine PM Emissions (pending estimation)
2.10.
4
.11 Fourteen Year Leaf Blower Fine PM Emissions (pending estimation)
5. Conclusion
In addition to surface characteristics, leaf blower emissions' fine PM components and
concentrations undoubtedly vary with detritus compositions, climate, weather and other
situational factors, and with leaf blower equipment characteristics and operator
performance. Regardless, the author believes the San Joaquin study sufficiently
representative to extrapolate its findings to the spectrum of fine PM emissions from leaf
blower operations.
Therefore, assuming its findings are representative, the substantial difference between
the 49.7mg/m3 San Joaquin study’s average leaf blower fine PM emissions, which
operators and proximate others inhale for the duration of each exposure and
cumulatively for multiple exposures, and the CalOSHA fine PM PEL of 20 mg/m 3, the
OSHA mineral dust permissible exposure limit (PEL) of 27.5mg/m 3 and the OSHA
average respirable dust PEL of 7.5mg/m3, there is strong reason to suspect that the fine
PM in a nationwide sample of leaf blower emissions would on average also substantially
exceed the legal permissible exposure limits intended to mitigate respiratory,
cardiovascular and cerebrovascular disease and mortality from the inhalation of these
particles.19
19
"Long-term exposure to combustion-related fine particulate air pollution is (also) an important environmental risk
factor for cardiopulmonary and lung cancer mortality." "Fine particulate and sulfur oxide--related pollution were
associated with all-cause, lung cancer, and cardiopulmonary mortality. Each 10-microg/m(3) elevation in fine
particulate air pollution was associated with approximately a 4%, 6%, and 8% increased risk of all-cause,
cardiopulmonary, and lung cancer mortality, respectively." "Lung cancer, cardiopulmonary mortality, and long-term
exposure to fine particulate air pollution", Pope CA 3rd, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K, Thurston
GD. JAMA. 2002 Mar 6;287(9):1132-41. Department of Economics, Brigham Young University, 142 FOB, Provo, UT
84602, USA. Cited in Wig Zamore, “Memo on Transportation, Air Quality and the Lovejoy Wharf Project RE: Draft
Environmental Impact Report / Final Project Impact Report FOR: Strada234 Residents Group”, April 26, 2006.
Significantly greater incidence of Tularemia in landscapers using power leaf blowers is also noteworthy. “Of
landscapers who used a power blower, 15% were seropositive, compared to 2% who did not use a power blower
(prevalence ratio 9.2; 95% confidence interval 1.2 to 69.0; p=0.02).” From: “Tularemia on Martha’s Vineyard:
Seroprevalence and Occupational Risk”, Centers for Disease Control and Prevention”, Katherine A. Feldman , Donna
Stiles-Enos, Kathleen Julian, Bela T. Matyas, Sam R. Telford, May C. Chu, Lyle R. Petersen, and Edward B. Hayes;
Emerging Infectious Diseases Journal (EID), Vol. 9 No. 3, March 2003
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