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Hazardous Air Inside |
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By Marwaan Macan-Markar
The
World Health Organization reports that one billion people are regularly
exposed to dangerous levels of indoor air pollution, whether at
home, at work or when traveling by mass transit.
MEXICO CITY - Every day of the week some four
million people descend into the belly of the sprawling Mexican capital
to board underground commuter trains, which ply from dawn until
after midnight along a network of over 160 km of tracks.
For passengers like Adriana Contreras Díaz,
29, a daily journey in Mexico City's Metro from home to the office
and back could mean spending well over two-and-a-half hours on board,
since she lives in the eastern end of this 1,479 square-km megalopolis
and works in the city center.
But how clean is the air she breathes during
the daily journeys in the Metro's cars? Are there times when the
air is polluted enough to lead to respiratory problems among the
passengers? What pollutants does this indoor air contain?.
At present, there are no clear answers to
these questions. But that is to change this December, when the National
Center for Environmental Research and Training (known by its Spanish
acronym CENICA) begins a four-month study of the quality of indoor
air in the Mexican capital's mass transport system, including the
Metro.
It is the first time an extensive study will
be carried out to assess the indoor air pollution levels in the
system, says Salvador Blanco Jiménez, the coordinator of Air Quality
Research at CENICA, a government organization. Experts are to test
for carbon monoxide, heavy metals, lead and particulate matter.
The winter months were chosen to conduct the
assessment because it is the time of year when pollution levels
in Mexico City's outdoor air are at their highest, adds Blanco Jiménez.
''We want to find out the difference and the relationships between
the outdoor and indoor air pollution during this period'', he explained.
The CENICA investigation can be understood
in light of concerns expressed by public health agencies around
the world about the high prevalence of indoor air pollution in homes,
offices and closed environments such as mass transport systems.
According to the World Health Organization
(WHO), nearly one billion people, most of them women and children,
are regularly exposed to levels of indoor air pollution 100 times
greater than the maximum established by WHO guidelines.
What is more, observes Dr. Peter Toft, manager
of special projects at the Health and Environmental Division of
the Pan-American Health Organization (PAHO), air pollution indoors
is 1000 times more likely to reach people's lungs than pollution
released outdoors.
And the consequences of such exposure have
led to a range of illnesses, including respiratory diseases like
asthma, chronic obstructive pulmonary disease, cardiovascular disease
and lung cancer.
Indoor air exposure to suspended particulate
matter (one of the most common air pollutants) increases the risk
of acute respiratory infections, affirms the Geneva-based WHO.
In India, for instance, where up to 80 percent
of households use solid fuels like wood, coal, charcoal and crop
waste for cooking, an estimated 500,000 children die annually from
indoor air pollution, particularly from acute respiratory infections,
according to the United Nations health agency.
And in the nations of sub-Saharan Africa, indoor
air pollution has been linked to an estimated 300,000 to 500,000
deaths annually.
While in Latin American countries, where about
one in four households regularly use solid fuels, the WHO estimates
that 30,000 people die each year from acute respiratory infections
attributable to poor indoor air quality.
But homes with modern fittings and state-of-the-art
offices are not immune from the problem of dirty air either. Indoor
air pollution can be a problem in Canada and the United States,
says Dr. Toft. It results from houses being sealed up, which causes
an accumulation of air pollutants that would normally escape.
According to a study conducted by the US Environmental
Protection Agency in select US schools, poor indoor air quality
(IAQ) was linked to children falling ill and blamed for acute health
symptoms that impaired their academic performance.
In addition, recent data suggests that poor
IAQ can reduce a person's ability to carry out specific mental tasks
requiring concentration, calculation or memory, states the EPA study,
Indoor Air Quality and Student Performance.
The WHO attributes such a rise in polluted
indoor air to the way modern buildings are designed. In an effort
to conserve energy, new design has favored tighter structures with
lower rates of ventilation, according to the agency's research.
In industrialized countries, important sources
of pollutants in indoor environments include the human body and
human activities, emissions from building materials, furnishings
and appliances and the use of consumer products.
In addition, the report also identifies inadequately
maintained heating, ventilation and air conditioning systems as
sources of indoor pollution.
Improper care of filters can lead to re-emission
of particulate contaminants. Biological impurities can proliferate
in moist components of the system and be distributed throughout
the building.
The situation is compounded further if the
indoor environment is polluted with tobacco smoke. The particle
and vapor phases of environmental tobacco smoke are complex mixtures
of several thousand chemicals, including known carcinogens, such
as nitrosamines and benzene, notes the study.
And Blanco Jiménez has evidence from Mexico
City that mirrors this conclusion. A CENICA study last year of the
indoor air quality in homes, schools and offices throughout the
Mexican capital revealed that smoking indoors had contributed to
an increase in the indoor air pollution levels, and more so in buildings
with poor ventilation.
In those structures with insufficient windows
and low ventilation, the pollution level can be higher than outside,
on the city streets, affirms Blanco Jiménez.
In that sense, Metro passenger Contreras Díaz
welcomes CENICA efforts to assess the air quality of the city's
underground commuter trains.
''You would think that the air is clean inside
the Metro, but it may not be so. It will be good to know just how
bad it is,'' she says.
Despite such concern, however, the Mexican
initiative is the exception to the rule. ''Most countries in the
developing world have yet to recognize indoor air pollution as a
hazard,'' remarks Dr. Toft.
* Marwaan Macan-Markar is an IPS correspondent.
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