Even a hundred years before Rudolf Diesel invented his engine in the 1890s, hydrocarbon soot was already known to be a danger in the workplace. Soot is the very first chemical substance ever identified as an occupational health hazard, being linked to diseases among chimney sweeps in London in 1775.
In America two centuries later, it's time to come to grips with the liability faced by fire departments that fail to take heroic measures to protect employee health.
Diesel smoke has been listed as a cancer-causing chemical by the state of California since 1990. It is a combination of chemicals which vary somewhat, depending on engine characteristics and fuel quality. All diesel smoke contains an array of substances, each by itself scientifically linked to cancer - arsenic, benzene, formaldehyde, nickel, and polycyclic aromatic hydrocarbons. Those toxic ingredients bind to the surface of microscopic particulate soot.
Numerous human studies demonstrate diesel exhaust exposure increases cancer risk. In fact, long term exposure to diesel exhaust particles poses the highest cancer risk of any toxic air contaminant evaluated by the California Office of Environmental Health Hazard Assessment.
Diesel engine fire trucks first appeared in the mid-1950s. Today, diesel power drives virtually all fire apparatus and emergency vehicles. Right from their introduction, the smoke that diesel apparatus emitted was regarded as unhealthy. At many firehouses some sort of tailpipe hose was jury-rigged to vent exhaust fumes outside through a window or under the door.
Nowadays - in addition to using the best available grade of fuel, minimizing running times, ventilating the building, exchanging fresh air, and keeping sealed doorways between garage and living quarters - there are limited ways of coping with the health risk of diesel smoke by building modifications in combination with aftermarket parts for fire apparatus.
Fans and filter cabinets remove airborne contaminants and help keep building surfaces clean, but since they do not prevent the release of particulates into the workplace atmosphere, they are janitorial equipment with no preventive health benefit.
Garage drop hoses and on-board diesel particulate filters are the two methods most often used to mitigate the hazard of diesel smoke in fire stations. Drop hoses are traditional and have some benefit, but you need to rethink whether drop hoses come even close to being adequate in light of today's environmental fervor.
Hoses require manual connection. Even brief exposure offsets air quality gains from a parked truck connected to a hanging hose.
Hoses are sometimes called capture systems, which is a misnomer. Hoses do not capture contaminants; hoses blow raw exhaust outdoors. Diesel soot is microscopic with a long airborne residency. Particles blown outside by a hose duct re-enter the building through doors which have to be open to allow the trucks in and out. This is called the canyon effect.
You'll never live to see the day a firefighter walks behind the wheels to try attaching exhaust hose to a moving truck. Hoses are not attached when a truck is entering the bay, nor do they stay attached when the truck goes out the door. Therefore, a hose system is not very effective at all.So then, beyond drop hose, what can a fire department do to ensure that its personnel are provided with the best available health protection? One study by a private advocacy group, the R.I.C.H.T.E.R. Foundation, which is dedicated to diesel exhaust safety issues, concluded, "The most efficient and cost effective way to reduce emissions is to install diesel particulate filters in all diesel trucks and equipment used in fire stations."
The California Air Resources Board is at the forefront of pollution control in the United States, and sets the standards by which local governments gauge compliance. CARB lists some diesel particulate filters as acceptable for emission reduction as aftermarket parts. No drop hose systems are listed because they are not considered pollution control devices.
On-board exhaust filters are not exactly a new idea. The first patent appeared back in 1908 when truck wheels had wooden spokes. In 1949 the U.S. Army invented the earliest version of the modern diesel exhaust filtration system.
In 1985 General Motors developed the monolithic ceramic honeycomb filter. Initial trials on high-end diesel Mercedes automobiles in the 1990s found the filters captured 99 percent of emissions. But back then, using available-grade diesel fuels, the filter captured so much soot so quickly that it had to be changed too frequently. Those experiments were abandoned, and the technology went more or less dormant.
With the coming of computerized engine ignition and ultra low-sulfur fuel, diesel particulate filters are much in vogue today.
The efficiency of the diesel particulate filter also poses its limitation. Filters clog. The rate at which they fill to capacity depends on fuel quality, the age and condition of the engine, and driving habits. Accumulation means periodic cleaning. As soot packs the filter channels, counter-pressure is created, which bogs down the engine. A close cousin of the diesel filter, in effect and principle, is the diesel exhaust brake, used on many heavy-duty trucks and buses.
A muffler is a silencer and also a spark arrestor. With a catalytic coating, it may be an oxidizer. Or used as a pre-filter.
Several manufacturers of diesel emissions systems use diesel particulate filters for over-the-road and off-road vehicles, including Englehard, Lubrizol, and Johnson Matthey. Those systems are, generally-speaking, complex and maintenance intensive. They impede horsepower through the "jake brake" effect, and all of them absolutely require burning ultra-low sulfur diesel fuel.
Most of our national awareness of environmental controversies originated on the West Coast, including pollution trade credits and the use of ultra low-sulfur diesel fuel. Current litigation foretells a brewing national movement that can have a crippling impact on fire departments large and small.
An open undecided lawsuit in California filed in May 2006 pits plaintiff Environmental Law Foundation (ELF) against Laidlaw Transit Services. The environmental activist organization demands school buses carry warning labels on all their buses, an extension of the way tobacco companies are required to label cigarettes.
The ELF lawsuit lays the groundwork for a flood of future big dollar claims related to occupational diesel smoke exposure. Plaintiffs argue that under health and safety laws, people have a right to be informed about exposure to chemicals that cause cancer, birth defects or other reproductive harm.
Health risks of diesel smoke are very real. The only sensible way to cope with diesel pollution in the workplace is to implement proactive steps that demonstrate the fire department is doing all that it can to ensure a safer workplace. Fleets must be converted eventually to new less-polluting fire apparatus as it comes to market. Short term, fire departments must retrofit existing apparatus with listed aftermarket pollution-control devices exhibiting the best technology.
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