Air Particles Linked to Cell Damage

[Cleanairbc] Air Particles Linked to Cell Damage
Dave Stevens geek@uniserve.com
Wed, 9 Apr 2003 22:08:37 -0700


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http://www.latimes.com/la-me-airstudy7apr07,0,679182.story
Air Particles Linked to Cell Damage
An L.A.-area study finds the tiniest pollutants disrupt basic cellular
functions, likely causing a host of diseases.
By Gary Polakovic
Times Staff Writer

April 7, 2003

A team of Southern California researchers has discovered that microscopic
airborne particles can disrupt the inner mechanics of cells, offering a
possible explanation of how air pollutants common in urban haze can harm the
human body.

The new study, led by scientists at UCLA and USC, links the most minuscule
particles found in dust and smoke to injuries. The particles are so small --
about 1,000 could fit inside the period at the end of this sentence -- that
they easily bypass the body's defense mechanisms.

The findings also are the first to show that very tiny particles travel beyond
the lungs and bloodstream to penetrate deep inside cells. The pollutant
accumulates within a critical component that powers the cell and maintains its
function. Damage to that cellular component is known to lead to an assortment
of diseases.

The study is scheduled to be published this week in the journal Environmental
Health Perspectives, a publication of the National Institute of Environmental
Health Sciences, and is currently available on the journal's Internet home page.

Researchers have long known that haze over major cities causes a wide range of
health problems. Numerous studies worldwide have linked particle pollution to
school absences, hospital admissions, shortened life spans, reduced lung
function, heart disease and cancer. The U.S. Environmental Protection Agency
established rigorous standards for curbing particle pollution in 1997. The
agency estimates that those rules will prevent 15,000 premature deaths, 350,000
cases of asthma and 1 million cases of lung problems in children by the year
2020.

But researchers have been unsure what types of particles were to blame for the
health effects.

"We have had no idea of the biological potency of different size particles in
the air," said UCLA researcher Andre Nel, a physician and lead author of the
study. The new research "may be a mechanism to explain how the smallest
particles cause adverse health effects," he said.

Particulate matter turns the sky gray with gauzy haze, limiting visibility. It
consists of microscopic bits, ranging from pulverized tire fragments to diesel
soot to acid droplets, and is measured in microns, a unit equivalent to a
millionth of a meter. A human hair is about 50 microns across.

Currently, environmental regulations try to limit particles that are 10 microns
in diameter and smaller particles in the 2.5-micron range. But the particles
that caused the most damage in the new study are one-tenth of a micron across.

Dust and smoke are made of particles of about 10 microns. The smallest
particles come mainly from burning fossil fuels. Those tiny particles float in
the air longer, travel farther and are more easily inhaled than larger ones.

The Los Angeles Basin ranks as one of the worst places in the nation for
particle pollution. The highest concentrations typically occur in western
Riverside County. But the Los Angeles-Long Beach area has more of the tiny
particles emitted by vehicle exhaust. Using the region as a laboratory, the EPA
established one of five national particle-pollution research centers at UCLA,
which produced the latest study.

In their study, the team of 10 scientists collected particles in various sizes
from air above Claremont and the USC campus near downtown Los Angeles between
November 2001 and March 2002. The pollution was concentrated, put into solution
and added to two types of cells.

One group of cells included macrophages taken from mice. A macrophage is a type
of cell that scavenges and destroys foreign matter in the lung and other
organs. The other cells were taken from the lining deep inside a human lung.
The scientists then measured chemical reactions in the tissues and examined the
cells with an electron microscope.

The researchers found that when the particles come in contact with the cells,
they trigger a reaction that causes inflammation. That may help explain how
particle pollution exacerbates asthma, an inflammation of the airways, Nel
explained.

Deeper inside the cells, researchers found that the one-tenth-of-a-micron
particles accumulated inside cell structures called mitochondria. Oblong in
shape, mitochondria are the workhorses of cells. They combine sugar and oxygen
to produce the fuel that keeps cells running.

The study shows that the pollution damaged the shape of mitochondria, causing
them to stop producing the cellular fuel and start producing other chemicals,
which lead to more inflammation and cell damage.

Melanie Marty, chief of air toxicology and epidemiology at the California
Office of Environmental Health Hazard Assessment, said the findings highlight
the danger of the smallest particles, which have not been the focus of
regulations of air pollution. She did not work on the research, but is familiar
with the paper.

"The mitochondria of a cell is like a cell's battery. Once you damage the
mitochondria, you're going to kill the cell," Marty said. "This shows the ultra-
fine particles are better at causing damage, and we should be paying more
attention to ultra-fine particles because of their toxicity and ability to
produce this stress in the cell."

The study comes with some limitations. Scientists examined pollutants at just
two locations in the Los Angeles region. Particle pollution varies by
concentration and type across cities.

Also, the pollution that the cells were exposed to in the study is more
concentrated than what is typically found in ambient air. The researchers
cautioned that their observations come from the laboratory and that more
studies are needed to see if similar results occur in people or animals exposed
to less-concentrated pollution.

Fernando Scaglia, a professor in the department of molecular and human genetics
at Baylor College of Medicine in Houston who has read the paper, said damage to
mitochondria in cells can lead to various diseases, including Parkinson's and
Alzheimer's, as well as strokes and other neurological impairment. Damage to
mitochondria, he said, can increase over time as cells divide, leading to a
breakdown of cell function and early onset of disease.




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