Control of air pollution has concentrated on major emission sources,
such as industrial plants, power stations, traffic exhausts, etc. However,
toxic substances only produce health problems when they reach the body,
and thus the effects of pollutants depend on a combination of concentrations
and human activity patterns. There has been a recent shift in focus
in pollution monitoring, especially by US Environmental Protection Agency
(EPA), which looks at patterns of human exposure to pollutants. This approach
has been permitted by the development of instruments small enough be worn
on the body, and sophisticated enough to detect levels of wide range of
harmful substances. Studies of more than 3,000 subjects in 14 US states
and 1 Canadian province tracked human exposure to 30 different Volatile
Organic Compounds (VOCs: hydrocarbons), PM10 (respirable particulates),
pesticides, and carbon monoxide. These studies strikingly showed that the
highest levels of human exposure occur indoors, not outdoors. The implications
of this work are profound: by focusing on which pollutant sources coincide
with the most serious exposure, esources can be targeted much more efficiently
on tacking pollution threats to human health.
Most people in developed countries spend much of their time indoors:
working, relaxing, eating, sleeping, so it is levels of pollution in indoor
environments that are most relevant to exposure levels. Exposure levels
may be very different from what would be expected from highest emission
sources.
Pollution associated with industrialisation has had severe effects
on workers in factories, where levels of pollutants may be very high. In
the 19th C., air quality was very low in many types of factory, from gases
and airborne particulates. The health problems associated with certain
trades were well known. For example, Lewis Carroll’s Mad Hatter was a charicature
of brain-damaged milliners who were regularly exposed to mercury vapours
(the American equivalent to the phrase ‘Mad as a hatter’ was ‘the Danbury
Shakes’, after the American centre of the hat industry).
Problems associated with particulates were especially severe, with high levels in many workplaces. In the 19th C., cotton mills had high levels of lint particles in air, leading to lung disease (byssinosis). Particulates severely affected cutlery grinders and miners in particular.
Case study I: coal mining
Coal mining has long been associated with serious hazards and health
risks, including explosions, fires and tunnel collapses. There are two
main air quality hazards: coal gas, and particulates. Coal gas is toxic
and highly flammable. The traditional 'miner's canary' was taken unbderground
to warn of coal gas hazards. When the canary died, it was time to get out.
Coal miners have long suffered health problems due to the inhalation of
fine coal dust particles, which lodge in the lung. Two principal diseases
are common among miners: emphysema and chronic bronchitis. Emphysema
is a lung disease involving damage to the air sacs or alveoli. The lungs
lose their elasticity and become less able to expand and contract. The
alveoli cannot deflate completely so less oxygen is taken into the lungs,
leading to breathing difficulties. Cigarette smoking is the most frequent
cause of emphysema but for the miners it was the coal dust which was held
to be mainly responsible for the disease. Chronic bronchitis is
an inflammation of the bronchi, the main air passages to the lungs. It
occurs over a long period and recurs over several years. The severity of
the disease relates to the amount and duration of the exposure to coal
dust and to a great extent whether the sufferer smokes cigarettes.
Compensation claims are proceeding against coal mining companies in Europe and North America. In the UK, the High Court awarded six miners up to £10,000 each in January 1998 for pain, suffering and disability from emphysema and chronic bronchitis. All but one of the claims were reduced because smoking contributed to the diseases, but the test case opened up the way for further action by 93,000 other miners.
Case study II: asbestos
Health problems due to various uses of asbestos have also become obvious
during recent decades. Asbestos refers to a group of minerals that
occur naturally as masses of strong, flexible fibres that can be separated
into thin threads and woven, or compressed into slabs. Four main types
were used: chrysotile, amosite, crocidolite (blue asbestos), and anthophyllite.
Asbestos is not flammable, is inert, and do not conduct electricity. For
these reasons, asbestos has been widely used in many industries and products,
including:
Generally, workers who develop asbestos-related diseases show no signs of illness until many years after first exposure. For example, the time between first
- Asbestosis - a chronic lung ailment that can produce shortness of breath and permanent lung damage and increase the risk of dangerous lung infections;
- Lung cancer;
- Mesothelioma-a relatively rare cancer of the thin membranes that line the chest and abdomen; and
- Other cancers, such as those of the larynx and of the gastrointestinal tract.
Many studies have shown that the combination of smoking and asbestos
exposure is particularly hazardous. Cigarette smokers, on the average,
are 10 times as
likely to develop lung cancer as are nonsmokers. For nonsmokers who
work with asbestos, the risk is about five times greater than for those
in the general
population. By contrast, smokers who also are heavily exposed to asbestos
are as much as 90 times more likely to develop lung cancer than are nonexposed
individuals who do not smoke. Smoking does not appear to increase the
risk of mesothelioma, however.
Many buildings still contain asbestos insulating materials, and the removal of such materials has to be done under very stringent conditions: was done in the Irvine Building (February 2000).
Case Study 3: Bhopal
Bhopal, India: Union Carbide Corporation pesticide plant producing Methyl Isocyanate (MC) began production in 1979.
On December 2, 1984, during routine maintenance, a large quantity of water entered storage tank. This caused a runaway reaction, in which temperature and pressure increased, and burst a tank, allowing MC gas to escape at 12.30 a.m. Cloud of heavy, poisonous gas enveloped the sleeping town, especially the shanty areas nearest the plant.
Safety systems were inadequate, and no warning was given to the communities in Bhopal until 1 hour after the leak.
According to government figures:
c. 3,800 people died,
40 experienced permanent total disability, and
2,680 persons permanent partial disability.
1989: Supreme Court of India directed Union Carbide Corporation (UCC) and UCIL to pay a total of $470 million
This money ws paid, but there are persistent claims that money did not reach the poorest people, i.e. those most affected. The number and conditions of victims is also contentious, some claiming that the death toll is still rising, others (i.e. Union Carbide) that there is no longer any problem.
This case study raises several important issues:
are safety standards less in the developing world?
do corporations meet their responsibilities there, as they would be
expected to in the west?
Victim support:
http://www.ucaqld.com.au/community/bhopal/
explain.html
Union Carbide story:
http://www.bhopal.com/
Good overview and reference list:
http://www.american.edu/TED/BHOPAL.HTM
Conditions in workplaces have improved in developed world in recent
decades, due to the introduction of comprehensive health and safety laws.
However, serious problems persist in 3rd world where legislation is less
stringent. Also, new hazards are continuously being identified, and workers
do not always choose to follow health advice. The modern office
presents many potential hazards in the form of solvents released from felt
pens, toner, correction fluid and inks. Levels of VOCs may be high in stationery
cupboards, and by photocopiers in poorly ventilated rooms.
Air pollution: home and recreation
Cooking and heating: an old problem, probably dating back to
the use of fire. Smoky fires produce soot particles and carbon monoxide
(C0) produced by incomplete combustion. Old or poorly maintained gas cookers,
heaters and boilers can be serious source of CO. Combustion also releases
sulphur and nitrogen oxides into homes.
Solvents, paints, building materials (particle board, chipboard,
plywood: bonded with resins, important source of VOCs in the home). Building
and decorating materials may leak toxic compounds into rooms for considerable
periods.
Dry-cleaned clothes: concentrations can be high in wardrobes where newly-cleaned clothes are stored. Can even cause death: case of child who died while sleeping in a dry-cleaned sleeping bag.
Carpets: New carpets can be a major source of VOCs; US EPA has entered
into negotiations with carpet manufacturers to reduce levels. Carpets (esp.
deep pile) are also reservoirs for toxic chemicals (e.g. insecticides such
as DDT) and fine particulates. Contribute substantially to exposure of
young children, who play on floors, crawl around on carpets, and regularly
put their hands in their mouths. Personal clouds created by disurbance
of fine particulates from reservoirs such as carpets and furniture by movement
of people, so that the exposure of a moving person is much higher than
recorded by a stationary instrument.
Radon is a naturally occurring radioactive gas, produced by decay
of uranium. Uranium is commonly found in granites, so it varies in natural
concentration according to geology. Radon is an unstable element, and decays
through a series of daughter products (isotopes of polonium, Lead, and
Bismuth), each of which releases either alpha or beta radiation (high velocity
helium nucleii or electrons, respectively). The daughters are short-lived
(seconds to days), but can be inhaled on dust, so radio decay releases
radiation directly into the lungs. Radon and daughters accumulate in poorly
ventilated homes following outgassing from rocks and soil, building stone,
or well water. In tightly-sealed, insulated homes in radon areas, concentrations
may be ‘00s or ‘000s times those outside. Overall, radon contributes about
half of total radiation exposure of public. Radon constitutes a health
risk by increasing levels of ionizing radiation, which may lead to lung
cancer. Risk established by studies of uranium mine workers, who suffer
elevated levels of lung cancer. EPA estimates that radon is responsible
for 5,000 to 20,000 cancer deaths annually.
Health effects associated with known or suspected airborne pollutants.
Building-related illness: May appear after single, high dose exposure or
repeated exposures: irritation of eyes, nose and throat, headaches, dizziness,
fatigue, triggering of athsma attacks. Treatment may simply consist of
removing person’s exposure to pollutant, if it can be identified, or improving
ventilation. Longer-term problems: cancers, heart problems and liver damage.
Sick-building syndrome: sometimes building occupants experience symptoms
which do not fit the pattern of any known illness and are hard to trace
to specific sources. However, distinction between SBS and BRI is blurring
as more causes are identified. Effects may be temporary or long term.
Sharp drop in indoor air quality when building ventilation was cut
in 1970s in attempt to conserve energy. Poor ventilation allows concentrations
to rise (e.g. around photocopier or in stationary cupboard).
Buildings related illnesses may be due to building materials, or unsuitable
operation, maintainance or ventilation of buildings. Problems may be due
in part to non-pollutant stressors: temperature, humidity, lighting, electromagnetic
fields, or social/psychological stresses. Multiple Chemical Sensitivity
BRI and SBS both incur large costs. Implicated by EPA as cause of up
to 5,000 cancers per year in US. Costs to economy: estimated $60 billion
in medical costs, loss of time from work, decreased work efficiency.
Remedies:
Improved ventilation. Ventilation promotes removal of pollutants, stopping
indoor air quality from reaching dangerous levels.
Use of plants to break down pollutants. Azaleas, rubber plants and
poinsettias tackle formaldehyde; lilies break down acetone, benzine.
Replacement of source materials. eliminating the sources of indoor
pollution requires adoption of greener technology: building materials,
paints, varnishes, etc. Such alternatives are available, but are currently
expensive and difficult to obtain.
References:
Ott, W.R. and Roberts, J.W. 1998: Everyday exposure to toxic pollutants. Scientific American, February, 72-77.
Back to Course Contents
Go to Doug Benn Homepage