by Lorin Hallinan
ou can hardly be on the freeway today without getting
stuck at some point behind a diesel exhaust trail. Who hasn't choked on
the insidious gunk belched into the air by trucks, buses or a show-off Mercedes
Diesel pollution is the dirty reality in our air space
that Rudolph Diesel never dreamed about when he invented the diesel engine
in 1893. To his credit, diesel engines are considered to be one of the world's
most efficient, and over the years improvements have been made to their
exhaust emissions. But then there's the dark side: Diesel engine exhaust
has been pegged as a potential health hazard.
The hit list
By law, the California Environmental Protection Agency
(CEPA), Office of Environmental Health Hazard Assessment (OEHHA) in Sacramento
has to update regularly the list of chemicals known to the state to cause
cancer or reproductive toxicity. The Safe Drinking Water and Toxic Enforcement
Act of 1986 (Prop. 65) requires that the governor revise and republish the
list of chemicals at least once a year. On Oct. 1, 1990, diesel engine exhaust
was added to the list.
In June 1994, the California EPA's Air Resources Board
staff put together a lengthy draft report titled "Proposed Identification
of Diesel Exhaust as a Toxic Air Contaminant." According to information
in the draft, diesel exhaust - an ominous-sounding mixture of gases, vapors
and fine particles - is considered a "potential or probable human carcinogen"
by several health agencies, including the National Institute for Occupational
Safety and Health, and the International Agency for Research on Cancer.
The agencies lump together several components under
the "diesel exhaust" umbrella. Some of the exhaust's components,
like arsenic, benzene, and nickel, are known to cause cancer in humans.
At least 38 other components of diesel exhaust have been listed as toxic
air contaminants by the Air Resources Board. Some of those harmful substances
include carbon monoxide, oxides of nitrogen, sulfur dioxide, particulate
matter, cyanides, metals and ammonia.
Diesel exhaust also came under scrutiny in a June 1994
preliminary report titled "Health Risk Assessment for Diesel Exhaust",
compiled by OEHHA and CEPA. The report states "the evidence that diesel
exhaust is carcinogenic in rats is clearly sufficient, and in humans the
evidence appears to be sufficient. OEHHA staff are considering the conclusion
that diesel exhaust is a human carcinogen" and that diesel exhaust
is "an air pollutant that may cause or contribute to an increase in
mortality or in serious illness, or which may pose a present or potential
hazard to human health."
Mobile sources are by far the primary sources of diesel
exhaust pollution. Heavy-duty trucks, urban buses, passenger cars and light-duty
trucks hauling people, products and assorted junk have all contributed to
the problem, emitting 41,500 tons of diesel exhaust particulate matter in
California in 1990. That's 70 percent of total emissions fouling the air.
Other sources, such as ships, trains, farm equipment, and construction equipment,
emitted 13,460 tons, or 23 percent the same year.
The good news is that the emission exhaust from mobile
sources in California is expected to decrease through 2010 because of emission
standards and regulations already adopted by the Air Resources Board and
the U.S. EPA. The problem is that by 2010, if no additional standards or
regulations are adopted, in light of blossoming population and more cars
on the roadways, the emissions are expected to increase, according to the
Air Resources Board's draft report.
A backseat concern
Alarm over diesel exhaust pollution has in the past
taken a back seat to other more high profile pollutants, such as ozone and
smog. Although diesel engine exhaust is considered a potential health hazard,
comments from staff at the California Air Resources board seem surprisingly
reserved. "Public concern is a little premature," said Jerry Martin,
public information officer for the board. "Right now, according to
what OEHHA is telling us, and what we measure, it seems that the average
Californian is not exposed to a high enough level (of diesel exhaust pollution)
to develop cancer from that exposure."
Although OEHHA states in its preliminary report that
diesel exhaust is toxic, it's toxic at a level that most Californians are
not exposed to, Martin pointed out. "If you were to breathe air which
contained five parts diesel soot per one million parts, and if you were
to breathe that for 24 hours a day, 70 years straight, you'd have the potential
for developing cancer solely from that exposure," said Martin. "That's
what OHEEA has said. There are some people, primarily those who work in
oil refineries, truckers, around ship ports and loading docks, that may
occasionally be exposed to those five ppm levels, but virtually no one we
know of is exposed to that level for 70 years nonstop.
"If you were to look at that draft report with
that understanding," he added, "you'd say that at current levels
in the state, very few people run a risk of developing cancer or birth defects
from exposure to toxic soot. But this is a preliminary report. As in any
draft report, it's subject to change."
Martin expects an updated report to be issued by the
board this fall. He also said that California is already forecasting stricter
emissions standards for diesel emissions. Right now, he said, diesel trucks
and buses are allowed to emit four grams of nitrogen oxide into the atmosphere
per hour of operation. By the year 2,002, that standard will be cut in half.
Least understood pollutant
The Air Resources Board is, however, clearly concerned
with what it calls PM10, a measurement of particulate matter 1/l0th to 1/50th
the width of a human hair.
Particulate matter is one of the compounds found in
diesel exhaust, and it defies simple definition. It's a hodgepodge of windblown
dust, scrapings off tires, fuel emitted from manufacturing plants, and other
compounds. It's the least understood of the major pollutants, according
to Martin, because it consists of so many different compounds, which vary
from place to place. In urban settings, there's more of it.
When you breathe in anything containing particulate
matter, your lungs suffer. They can't effectively stop or deflect all that
pollution, which can deposit itself well into the lung tissue, increasing
the potential that you'll get sick or find respiratory illnesses like asthma,
emphysema or bronchitis, getting worse.
A better way
According to Roger Pieplow, marketing director for Clean
Air Partners Inc., a designer, manufacturer and marketer of conversion systems
in San Diego, all engines - gasoline and diesel - can be adapted to run
on natural gas or run on a bi-fuel system, with natural gas being half of
the fuel source.
If all engines ran on readily available natural gas
fuel, the company's literature points out, the United States could reduce
fuel cost by $60 billion annually, reduce automotive pollution by 80 percent,
eliminate dependence on $50 billion of imported oil every year, and create
four million new jobs.
Natural gas burns fuel cleaner than diesel and gasoline,
does not emit particulate matter, and is less expensive to process, although
it takes more physical space to store than gasoline or diesel fuel. "Take
natural gas out of the ground, filter it, dry it, and it's ready to go,"
said Pieplow. "You have to refine gas and diesel fuel."
Hawthorne Power System in San Diego, which sells tractors
and engines, provides natural gas engine conversions at its Kearny Mesa
division. According to Scott Smith, product support representative, it costs
about $4,000 to $6,000 to convert a gasoline engine, and $7,000 to $9,000
to convert a diesel engine. Obviously, the average consumer isn't likely
to spend that kind of money for a conversion, but commercial vehicle owners
have an incentive.
Pushing for change
According to the 1992 Energy Policy Act, federal legislation
requires certain fleet operators who own 10 or more motor vehicles to use
alternative fuels when they purchase new vehicles. The requirements began
phasing in last year and will continue to be phased in through 1999, according
to Howard Levin, alternative fuels marketing manager at the San Diego Gas
& Electric Co.
SDG&E has put into place programs that help demonstrate
to local fleet operators the value of natural gas, that it's cheaper and
cleaner to use. While only nine consumers in the county drive privately-owned
natural gas vehicles, there are over 700 commercial vehicles in San Diego
powered by the alternative fuel source, according to Levin, including trucks,
transit buses, school buses, vans and even one street sweeper operated by
SDG&E operates 13 public natural gas fueling stations
in San Diego County, seven on SDG&E property and six at regular retail
gasoline sites, such as Shell, Mobile and Texaco gas stations.
At this point, there aren't enough alternative fueling
stations available to make the cost worth a consumer's while. But it's getting
easier for commercial vehicles to fill up. Natural gas fueling sources operated
by SDG&E are strategically located around the county in Carlsbad, Encinitas,
Vista, Escondido, Poway, Rancho Peñasquitos, Kearny Mesa, Miramar,
El Cajon, Chula Vista, Otay Mesa, downtown San Diego, and Coronado.
In 1994, the stations dispensed 476,000 therms of natural
gas, or the equivalent of 400,000 gallons of gasoline at 75 cents per therm,
or the equivalent of 88 cents a regular gallon.
Depending on Utility Commission approval, Levin said SDG&E plans to
do a number of things to promote alternative power sources. "We want
to develop programs to educate customers about electric vehicles, too,"
Is it likely that natural gas will replace other fuel
sources entirely any time in the near future? "I can't really fathom
it totally replacing petroleum products," said Levin. "There are
81/2 billion 42-gallon barrels of petroleum products used for transportation
every day in this country."
With the help of federal and state mandates dictating
alternative fuel usage, and continuing study conducted by state government
agencies, diesel exhaust pollution should pose less of a potential health
hazard in the future. But it's too early to breathe easy just yet.
Lorin Hallinan, a regular contributor to Earth Times, is a freelance
author and former editor for the Coast Dispatch and Carlsbad Journal community
newspapers. A 13-year San Diego resident, she lives in Carlsbad.
If you spot a smoking vehicle on the roadway, you can
do something about it. Call the San Diego Air Pollution Control District's
toll-free 24-hour smoking vehicle hotline at (800) 28SMOKE. A recorded message
will ask for the following information:
Your report will help get pollutiong cars and trucks
off the roadways.
- License number
- Date and location vehicle was spotted
- Color and type of vehicle
- Your name and phone number (optional)