Amonia Pollution Linked to
Reformulated gasoline and catalytic
converters introduced to reduce pollution may contribute to a
different type of pollution - ammonia. Researchers have found
evidence that cars may be the main source of haze-inducing ammonia,
rather than livestock, as previously thought.
In a study of 4,500 vehicles conducted
on a southern California freeway ramp, researchers found unexpectedly
high levels of ammonia in the cars' exhaust emissions. The researchers
estimate that cars are adding twice as much ammonia to the air
of California's southern coastal basin as livestock do.
Ammonia plays a role in the formation
of very small airborne particles, sometimes called "particulate
matter." The U.S. Environmental Protection Agency recently
targeted such particles for regulation under Clean Air Act standards
on the grounds that they endanger human health.
Until now, scientists believed that
decomposition of livestock waste was the main source of atmospheric
ammonia. Some theorize that reformulated gasoline, introduced
in the mid-1990s to lower sulfur and other emissions, has contributed
to the increase in ammonia levels.
The evidence also suggests that a small
share of the vehicles in the study produced most of the pollution.
It was found that 70 percent of the vehicles had detectable ammonia
emissions, but just 10 percent generated 66 percent of the total
Using a measuring technique called remote
sensing, the research team collected information on ammonia emissions
on a car-by-car basis. This information, along with snapshots
of the cars' license plates, enabled them to pinpoint the make
and model of vehicles responsible for the elevated ammonia levels.
Aside from cars and dairy farms, major sources of ammonia emissions
include fertilizers and sewage treatment plants.