Industrial activities are a major source of air, water and land pollution, leading to illness and loss of life all over the world. Pollution is a slow, continuous process. Some illnesses take 20 years to manifest
Industrial activities are a major source of air, water and land pollution, leading to illness and loss of life all over the world. The World Health Organisation estimates that outdoor air pollution alone accounts for around 2% of all heart and lung diseases, about 5% of all lung cancers, and about 1% of all chest infections.
One of the worst industrial disasters of all time took place in Bhopal , India , in December 1984. In the three days after the first leak occurred, around 8,000 people died. Many thousands more still feel the effects two decades on.
While Bhopal was a single event that caused the death of thousands of people in a very short period of time, pollution is often a slow, continuous process. An example is air pollution caused by industrial activity, motor vehicle exhaust and the burning of household stoves. Research on the relationship between levels of daily outdoor air pollution and the prevalence of diseases, based on hospital admission reports, shows that for every 10 microgram increment in the concentration of respirable particulate matter in the air, the risk of death from respiratory illness increases by 1%. Inside homes, air pollution caused by burning fossil fuel (such as coal or wood), used in many Indian households, is linked to tuberculosis and respiratory illnesses among women and children. Worldwide, indoor air pollution accounts for about 34% of all respiratory illnesses.
In all these situations an excess of substances in the environment is responsible for either death or illness among people exposed to them. In the case of Bhopal it was a gas that leaked out of a factory; in air pollution it is tiny particulate matter that penetrates deep into the lung tissue.
Pollution and pollutants
A simple definition of pollution could be the presence of high quantities of any entity in the wrong place. This indicates that a specific substance cannot in itself be labelled a pollutant. It becomes a pollutant when concentrations of the substance are too great to sustain health in any given place. For example, high concentrations of respirable particulate matter in lung tissue harm the respiratory system. Another example is inorganic arsenic. When concentrations of inorganic arsenic exceed 10 micrograms/L in the groundwater, significant adverse health effects occur in people who consume that water.
Pollutants are present everywhere in our environment and enter our body through the air we breathe (respiratory system), the food we eat and water we drink (gastrointestinal system), or through skin contact.
Pollutants affect our health in several ways. These include direct irritation of target organs or metabolic changes within cells. For example, exposure to too much smoke, fumes or dust evokes a burning sensation in the airways, tightness in the chest and possible suffocation. Sometimes, the effects are subtler and may take years to develop. Asbestos fibres, for example, are small needle-shaped silicate crystals that penetrate deep into lung tissue and evoke reactions. It takes around 20 years for some illnesses to manifest.
Other health effects involve metabolic pathways in our bodies -- pathways of chemical reactions in our cells -- where they may interfere with energy production or cellular repair mechanisms. For example, exposure to inorganic arsenic is common among people who work in copper smelters or live around them. Exposure to inorganic arsenic also occurs among people who consume water from shallow tubewells in areas where the groundwater contains high levels of inorganic arsenic.
When it enters the body, inorganic arsenic is transformed through the same chemical reactions that are necessary to maintain the repair processes of DNA molecules within the cells. As a result of excess exposure to arsenic, and demands on these reactions, faulty repair of DNA molecules causes tumours to form.
How do we learn about the health effects?
Industrial pollution is non-specific. Exposure takes place subtly and the observed health effects are, often, common symptoms. Unless physicians are specifically aware of the ‘industrial’ causes of diseases and look for them, they are likely to miss the signs. Sometimes, though, the symptoms are severe enough to warrant a search for possible exposure to specific industrial pollutants. Therefore, a high level of awareness about the possible links between health and pollution is necessary to link symptoms to exposure to industrial pollutants.
Epidemiology is a study of the distribution and causes of diseases in populations, and methods to control them. Epidemiologists study and link health effects with industrial pollutants using various methods. Based on the amount and quality of information they generate, they can be ordered from ‘least informative’ to ‘highly informative’ as follows (also ‘least expensive’ and ‘highly expensive’):
Case studies and case series: A case study or description of a series of case studies is a purely descriptive method to link exposure to outcome. For example, descriptions of illnesses of people who lived close to the Union Carbide factory in Bhopal , following the Bhopal gas disaster, would qualify as case series studies.
Cross-sectional surveys: These tend to provide a ‘snapshot’ of the health experiences of people who are exposed to industrial pollutants. In cross-sectional surveys, people are asked about their health and the diseases they suffer, while measurements are simultaneously taken to evaluate their exposure to industrial pollutants. This information is then analysed. Although such studies provide important hints about the cause-and-effect link between industrial pollution and health, they cannot be definitely used for cause-and-effect analyses.
Case control studies: Here, people suffering from illnesses (‘cases’) are matched with similar healthy people (‘controls’) and are compared for exposure to industrial pollutants. If the risk of exposure to an industrial pollutant is much greater among the ‘cases’, as compared to the ‘controls’, this supports a cause-and-effect linkage between exposure to the industrial pollutant and its effects on health.
Cohort studies: Here, cohorts (or groups) of healthy people are followed over time. One of the cohorts is exposed to the industrial pollutant. Over time, rates of disease development are measured in both cohorts and compared. The assumption is that relatively greater risk of disease occurrences will be observed among the exposed population. Researchers who have studied the health effects of the Bhopal gas disaster have used this approach.
Even though industrial pollution is harmful to health, both the sources of pollution and the resulting health effects are preventable. Prevention calls for the identification of polluting sources, awareness about the links between pollution and health, and steps to minimise the risks. These could be in the form of policy and regulatory controls by the government, improved technology to minimise industrial pollution and the adoption of personal protection.
World Health Organisation. Global estimates of burden of diseases caused by environmental and occupational risks. http://www.who.int/quantifying_ehimpacts/global/urbair/en/
Samet, J M. National Morbidity, Mortality, and Air Pollution Study. Health Effects Institute, Boston, 2000
InfoChange News & Features, December 2004