Hello phizzy,
Good question. I had wondered about the same thing myself. I found the
following articles which I think you will find interesting:
http://cartalk.cars.com/Columns/Archive/1994/August/07.html
Dear Tom and Ray:
According to the book "50 Simple Things You Can Do To Save The Earth,"
every two weeks, Americans wear almost 50 million pounds of rubber off
their tires, enough to make more than three million new tires from
scratch. Now, I dodge pieces of blown semi-trailer tire every day on
the interstate, but I don't think that's what they're referring to.
They're talking about normal wear. I'd really like to know what
happens to all that WORN rubber. Is it embedded in the roadway in
microscopic pieces, or does it gas-off into thin air? And is it
harmful to the environment? Victor
Ray: That's a very good question, isn't it Victor? That's a lot of
rubber. And you don't see it on the road (except near high schools,
where teen age boys peel out). So where is it going?
Tom: Well, it turns out that this is one of the great mysteries of the
late 20th century.
Ray: We talked to the Rubber Division of the American Chemical
Society. They confirmed that researchers really don't know exactly
what happens to the rubber that comes off tires.
Tom: They told us an early concern was that it was coming off in a
gaseous state--as air pollution. But all the research they've seen
indicates that very little of the tire ends up in the air. And the
amount that does represents much less of a pollution threat than the
stuff that comes out of tailpipes.
Ray: Their best guess is that the majority of the rubber--which comes
off in very small particles--ends up on or by the side of the road.
And that it is broken down naturally--or converted back into the
natural carbon cycle by oxidation, photoexcitation, and enzyme
catalysis--aka "nature."
Tom: A German study recently claimed that not all tire residue
disappears. It found that several pounds of heavy metals from tires
are found by the side of highways each year. But that study is being
disputed.
Ray: So what can you do vis a vis tires if you want to "save the
earth?" I'd say you'd be best off encouraging the development of
technologies that recycle USED tires that come off of cars. That
represents far more rubber than what's being left by the side of the
road.
http://www.rachel.org/bulletin/bulletin.cfm?Issue_ID=686&bulletin_ID=48
We all know some of the consequences of converting the American
transportation system from electric/rail to rubber-tired vehicles. The
threat of global warming from combustion of fossil-fuels (oil and
gasoline) is one part of the problem. Lung cancer from diesel exhaust
is another.[2] But recently, another aspect of our transportation
system has appeared in scientific and medical literature: serious
pollution from rubber tire fragments (tire dust) released by tire
wear.
When a rubber tire, bearing the weight of a vehicle, rolls across an
asphalt or cement surface, tiny fragments of rubber break off from the
tire and become airborne. In the 1970s and early 1980s, scientists
working for the rubber tire industry and for the U.S. Environmental
Protection Agency concluded that these tire fragments were too large
to enter the human lung and so presented no threat to human health.
However, new research published this year by allergy specialists has
reached a different conclusion: these new studies show that about 60%
of tire fragments (tire dust) are so small that they can enter the
deep portions of the human lung where the latex rubber in the tire
dust may cause allergic reactions ranging in severity from rhinitis
(runny nose), conjunctivitis (tearful eyes), to hives (urticaria),
bronchial asthma, and occasionally even a life-threatening condition
called anaphylactic shock.[3] Asthma, and asthma deaths, have
increased dramatically during the past 20 years, especially among
children, and specialists have been searching in vain for causes. (See
REHW #374.)
Allergy to latex rubber has become more common in recent years,
especially among health-care workers who are exposed more or less
continuously to latex gloves, tubes, sheets, and other
latex-containing products.[4] An estimated 17 million Americans have
an allergic reaction to latex. Examination of latex allergy has shown
it to be a true allergy; in technical jargon, it is mediated by IgE
antibody to proteins that are present in the natural rubber produced
from the tropical rubber tree (Hevea brasiliensis).
Allergic reactions to tire dust may be increasing for several reasons.
The number of tires has increased steadily during the last 20 years;
the proportion of latex in tires has been increasing; and tire
construction has changed from bias ply to radial. Tire dust from
radials is finer and thus more respirable, meaning it enters the
deepest part of the human lung more easily.
The human nose and throat filter out airborne particles larger than 10
micrometers in diameter, but about 60% of tire dust is smaller than 10
micrometers in diameter and can thus enter the lungs where it can
cause allergic reactions in some people.
In 1974, when there were 524.3 million tires in use in the U.S. (on
cars, motorcycles, trucks, and buses), tire industry scientists
estimated that 600,000 metric tonnes (1.3 billion pounds) of tire dust
were released by tire wear in the U.S., or about 2.5 pounds (a little
over one kilogram) of dust released from each tire each year. In 1991,
there were 782 million tires in use in the U.S.; if each tire releases
2.5 pounds of dust per year, tire dust released in 1991 would total
1.9 billion pounds. A billion is a thousand million. In Los Angeles
alone, at least 5 tons (10,000 pounds) of tire dust are released into
the air each day.
Radial tires create a finer, more respirable dust than do bias ply-
constructed tires, and the percentage of tires that are radial grew
from 2% in 1970 to 95% in 1990, so tire dust released in the 1990s
probably enters the lungs more readily than tire dust did in previous
decades. Conceivably, this might explain part of the recent increases
in asthma in the U.S.
In 1994, careful measurement of air near roadways with moderate
traffic revealed the presence of 3800 to 6900 individual tire
fragments in each cubic meter of air, more than 58.5% of them in the
fully-respirable size range. When these fragments were examined
chemically, and by mass spectroscopy, they were shown to contain
latex. Furthermore, they were shown to produce allergic reactions,
comparable in every way to the allergic reactions caused by dust from
a pulverized latex glove.[3]
How might these problems be resolved? Allergic reaction to latex was
first described in 1979; after AIDS became a major medical problem,
more and more medical workers started wearing latex gloves and latex
allergies came to light. Some 7% to 10% of all health care workers now
exhibit an allergic reaction to latex.
Recently, latex from a new source, the guayule plant (Parthenium
argentatum), which grows well in the southwestern U.S., has been shown
to not cause latex allergy in exposed people.[6] Latex from the
guayule plant could become a growth industry for American farmers;
presently, about seven million tons of latex are produced each year
from the tropical rubber tree, Hevea, worldwide.
In the case of rubber tires, the problem is more complex than mere
latex allergy, although this may well turn out to be a serious public
health problem by itself. The high dollar cost of truck freight,
private automobile commuting, and maintenance of our highway
infrastructure must be counted as major sacrifices to our rubber-tired
transportation system. Furthermore, fine particle air pollution now
kills an estimated 60,000 Americans in cities each year.[7] And global
warming is a serious threat to many nations from many viewpoints. (See
REHW #429, #430.)
However, from the viewpoint of our most important national treasure --
our self-governing democracy --the systematic sabotage of the nation's
electric/rail mass transit systems by automobile corporations points
up a most serious problem: the ability of "private" corporations to
effect sweeping changes in our public life and culture, without public
accountability or even debate. If we ever hope to achieve a
sustainable environment, and re-establish a fair economy and a working
democracy, this is a key problem we will have to acknowledge and
address.
http://www.sciencedaily.com/releases/2002/11/021126204056.htm
What Happens To Rubber That Wears Off Auto Tires?
Alison J. Draper, an assistant professor of chemistry at Bucknell
University, Lewisburg, Pa., is doing research where the rubber meets
the road -- literally.
She's investigating the environmental and health impacts of automobile
tire wear particles. As automobile tires move along a road, tiny
particles are worn off, and can end up in the air and in nearby
waterways. Draper previously did research on diesel exhaust, but says
that tire rubber is "much more interesting chemically," containing
heavy metals like zinc and cadmium, hydrocarbons, latex, and
sulfur-containing compounds.
Draper's research is not yet complete. But so far her findings include
preliminary but solid evidence that tire wear particles may have
negative impacts on small organisms in water habitats. Airborne tire
particles may also aggravate respiratory problems in human beings
(such as asthma or allergies).
Draper's method has been to make up clean samples of water like those
inhabited by several kinds of aquatic organisms -- algae, duckweed,
daphnia (water fleas), fathead minnows, and snails -- and under
controlled laboratory conditions, put finely ground tire particles
into the samples. By letting the particles remain in the water for 10
days and then filtering them out, she created a "leachate" that
included substances in the tire rubber. All the organisms exposed to
the leachate died, and the algae died fairly quickly.
Draper is also working on determining the levels of tire rubber
chemicals in water that cause sub-lethal effects, such as reproductive
problems in the snails and pre-cancerous lesions in the minnows.
Draper's work so far has been performed in a lab, under controlled
conditions, but she says there's "good evidence" that tire rubber may
have similar effects on similar organisms living in real waterways
along real roadways.
An environmental chemist with a doctorate in toxicology (University of
Kansas Medical Center, 1996), Draper is also the Clare Boothe Luce
Professor of Environmental Chemistry at Bucknell. She says there's
good evidence from the chemistry of tire rubber that it also has the
potential to cause asthmatic and/or allergic-type reactions. "We're
only at the very beginning of that investigation. But, given the
chemicals in tire rubber and given how readily they leach out, we can
expect a respiratory response [in human beings]," she says. "It
depends on the levels of the chemicals and the level of exposure --
certain people will be more susceptible than others."
Draper's research started humbly, with an old tire that came from her
father's 1981 Chevrolet Malibu and was already on the refuse heap. "My
father was about to throw it out," Draper recalls, "and I said,
'Wait!' " Now she uses tire tread particles supplied by a company in
Mississippi, already ground up, and consisting of mixed tire brands.
It sounds to me that there is still more research to be done to fully
understand the entire impact of tire wear particles on our earth.
Perhaps when Alison J. Draper completes her study we will know more.
Hope this answers your question, Redhoss |
