Air pollution: the silent killer


By Prof. O.A.Ileperuma,

Emeritus Professor,

University of Peradeniya

An average person consumes about 1-2 kg of food, 1-2 litres of water and breathes about 10,000 litres of air daily. While we are cautious about the hygienic aspects of food and water, do we ever care about the quality of air we breathe? Breathing poor quality air brings about a host of health problems such as asthma, bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. In addition to these respiratory diseases, more recent evidence suggests that it is related to various heart diseases and stroke, low birth weight of babies, premature deaths and obesity. World Health Organisation (WHO) claims that 92% of the people in the World do not breathe clean air and around 8 million deaths annually can be attributed to air pollution with 4.3 million deaths from indoor air pollution and 3.7 million deaths from outdoor air pollution. Worldwide, air pollution related deaths have now overtaken water pollution as the leading cause of child deaths. In Sri Lanka, too over 45% of the admissions of children to hospitals are due to air pollution.

Air pollution is the introduction of chemicals, particulate matter or biological materials into the atmosphere that cause harm or discomfort to humans, other organisms or damage the natural vegetation and structures. An air pollutant can be defined as a substance present in a sufficient concentration to produce a harmful effect on humans and other animals, vegetation or materials. Air pollution in Sri Lanka arises mainly due to exhaust gases from motor vehicles and also from various industries, power plants and burning of waste and biomass.

Fossil fuel combustion produces a large amount of carbon monoxide and elemental carbon in the form of soot, sulphur dioxide and nitrogen dioxide. Some of these like the oxides of nitrogen and sulphur are harmful corrosive pollutants which destroy the protective layer of the lung tissues making it more vulnerable to attack by bacteria and viruses. They can cause the respiratory diseases mentioned above and in addition we have to consider the various heart problems of specially elderly people who may be affected by air pollution. Out of these pollutants, fine particles in the form of soot from vehicles represent the most dangerous pollutant. Particles larger than 10 microns in diameter (a micron is one millionth of a metre) are filtered through the nose and the upper respiratory tract while those smaller than 10 microns go right inside the lung. This fraction is called PM10 fraction and even smaller particles with diameters less than 2.5 microns called the PM2.5 fraction is even more hazardous.

Air pollution is considered to be the main cause of premature deaths in the world. Out of major global health risks, outdoor air pollution in the form of fine particles is found to be much more dangerous for public health than what has been previously known and contributing annually to over 2 million premature deaths worldwide. What is more significant is that a global WHO study ranks air pollution as one of the top 10 killers in the world, with 65 percent of all air pollution deaths occurring in Asia. In 2010 alone, particulate matter pollution was the fourth-leading risk factor for deaths in China, behind high blood pressure and smoking. In the year 2008 alone, over half a million people have died in China and India owing to air pollution. By 2050, urban air pollution is estimated to cause up to 3.6 million premature deaths worldwide each year, mostly in China and India.

In many Asian cities the levels of fine particulate matter - a key pollutant in terms of its impact on human health are exceeding the critical limit (as defined by the WHO), specifically in densely populated, fast-growing and less developed countries like China, India, Pakistan and Bangladesh. Even in small Asian cities like Kathmandu, the particulate matter level exceeds the rather lenient standards recommended by the WHO.

Air pollution in Sri Lanka

According to statistics compiled by Prof. Amal Kumarage of the Moratuwa University , on an average, 300,000 vehicles, made up of 15,000 buses, 10,000 trucks and 225,000 private vehicles, enter the Colombo city daily. There are 7.24 million vehicles in Sri Lanka out of which 4.04 million are motorcycles with 1.14 million three wheelers and 600,000 vehicles are registered every year. Number of vehicles registered has increased by nearly 14 fold between 1990-2010 while the number of three wheelers and motorcycles increased by a whopping 600% during the last twenty years. The lack of a proper high quality public transport system has resulted in over 50% of the working population to use private vehicles to commute to work. Average speed for vehicles in Colombo was 22 km/hour in 2012 while it is now 17 km/hour. Vehicles travelling in traffic jams produce more fine particles in the form of soot which adversely affects our health.

Last year WHO classified diesel fumes as a Class1 carcinogen which means that these can definitely cause cancer. There are two kinds of poisons; acute and chronic. An example of acute poisoning arising from air pollution can be the triggering of asthma in asthmatics or increased hospitalisation due to breathing difficulties. In 2005, WHO has calculated that more than 20% of hospital admissions to the Lady Ridgeway hospital due to asthma can be correlated to the PM10 values in air. An earlier study in 2004 correlated increased admissions of children with asthma requiring nebulisation to the same hospital on days where the sulphur dioxide levels were high. Chronic poisons are those which act over a longer period and these are the real silent killers. The fine carbon particles from motor vehicles represent the most dangerous type of pollutant. Not only do they damage the sensitive protective layer in the alveoli of lungs, these carbon particles have many cancer causing substances which we call polyaromtaic hydrocarbons attached to fine particles. Accumulation of such compounds over a number of years can increase the rate of cancer and this is the reason why exposure to diesel exhaust fumes can be considered as a silent killer.

Recently WHO in collaboration with the Climate & Clean Air Coalition (CCAC) released air quality data for 3,000 cities and towns globally and according to the data 80% of the cities around the world have exceeded the safe air quality levels. This study shows that air pollution levels in the Colombo city limits have exceeded the WHO safe level of 10 microgrammes/m3, by 3.6 times which is quite alarming compared to some of the other cities. In Colombo PM2.5 levels recorded are 36 microgrammes/m3 while for the whole country this value is 22 microgrammes/m3. This study further states that 7792 people die from an air pollution-related disease each year and the top illness caused by air pollution is ischaemic heart disease. Another study has compared the relative risk of heart attacks caused by different factors and staying in one hour of traffic is the leading cause (relative risk 3.9) followed by high cholesterol (3.7), anger (3.1), smoking (2.8), diabetes (1.8) and physical inactivity (1.4).

By contrast, cities in the developed world fare much better wheree the PM2.5 levels are much lower. For example, New York city which has a far higher number of vehicles has an annual average of 9 microgrammes/m3 and London with a value of 15 microgrammes/m3 which is slightly higher than the safe level but nowhere near the values in Colombo. The reason is that these cities in the west have better roads and transport systems and discourages car travel.

Indoor air pollution

People spend more time in indoor environments compared to outdoors. There are several ways by which the air inside our homes can get polluted and some of these factors are: kitchen smoke, cigarette smoke, solvents, sprays, formaldehyde (from adhesives in furniture), radon from granite and burning mosquito coils and incense sticks inside homes. Out of these, firewood burning in congested kitchens produces the most dangerous pollutants to our health. Burning firewood produces an enormous amount of carbon monoxide which causes headaches due to reduced oxygen supply to the brain and also a lot of fine particles which cause cardiovascular diseases (strokes, ischaemic heart diseases in addition to respiratory diseases). Mothers who spend a lifetime in congested kitchens develop lung cancer in later stages of life as a result of being continuously exposed to kitchen smoke for years. Lung cancer is generally caused by heavy cigarette smoking and occurrence of lung cancer in elderly woman is most likely due to exposure to firewood smoke. In India, it has been found that 50% of ill-health in women is due to exposure to kitchen smoke while 35% of diseases in children, who usually hang around their mothers is also due to air pollution. Men are free from such effects since they are inside the living room or outside the home chatting with their friends.

Scientists in Sri Lanka have carried out indoor PM2.5 measurements from 132 urban homes using cleaner fuel such as LP gas in Colombo and found that these homes had a mean concentration of 84.4 microgrammes/m3 from PM2.5 in the living area. Similar measurements were reported from homes that burned firewood for cooking in an urban setting with a mean of mean of 243.2 microgrammes/m3. These values exceed the Sri Lanka standard of 25 microgrammes/m3 for PM2.5 although the WHO standard is much stricter at 10 microgrammes/m3.

Another huge problem is mosquito coils used by 2 billion people worldwide who burn 12 billion coils every year. A mosquito coil has pyrethroids, coal dust/coconut husk, binders such as cow dung and resins in its composition. It has been estimated that burning 1 mosquito coil produces enough PM2.5 particles as 100 cigarettes and as much hydrocarbons produced by 50 cigarettes!

Burning incense sticks produces around 20,000 microgrammes/m3 of PM2.5 after a few hours where the tolerable level is only 10 microgrammes/m3. Both mosquito coils and incense sticks produce polyaromatic hydrocarbons and benzene which are known carcinogens. It is not advisable to burn them inside homes specially when babies are present since they breathe more air relative to their body weights than adults. Due to these reasons people should be educated to have the firewood kitchens in an open space outside the main house.

Pollution in Asian cities

According to an ADB report, "Asian cities have made dismal progress over the last 10 years with increasing threat to human health in Asia’s cities and of the world’s 15 most polluted cities 13 are in Asia. Asia’s environment is so polluted and degraded that it poses a threat not just to the quality of life but also to its economic prosperity". Earlier Beijing was the most polluted city on Earth but now New Delhi has got the dubious distinction as the most polluted city on Earth. This is mainly due to the excessive fine particles generated to the atmosphere from buses and cars and traffic jams. In some areas, Delhi, particularly during festivals like Diwali, PM2.5 levels increased to 1,238. WHO has declared that exposure to average annual concentrations of PM2.5 of 35 or above is associated with a 15% higher long-term mortality risk.

Air pollution and Government inaction

The city of Colombo is in a way lucky to have been located close to the sea where the pollutants get dispersed over the flat terrain. However, there are so many traffic jams throughout the day giving out an enormous amount of air pollutants into the atmosphere. Unfortunately we have no way of knowing whether we breathe clean air since the air quality monitoring station located at Colombo Fort has been inoperative since 2002 owing to a lack of spare parts for the instruments measuring air pollutant levels. This is an atrocious excuse considering that millions are spent on importing luxury cars for the politicians and the Ministry of Environment coming under the President cannot find a few thousands to monitor air quality. The equipment in question was obtained from World Bank funds in 1996 and ceased its operation by 2002.

Most countries have automated air quality monitoring stations in all major cities. Most of the big cities have several such stations to represent different areas such as commercial and residential areas. Even smaller cities have at least one air quality monitoring station. These monitoring stations typically monitor five important air pollutants where a sample of ambient air is taken every 5 or 10 minutes. They are automatically sent through different instruments to determine pollutant levels and the data are recorded automatically to be transmitted to a central office dealing with air quality. Data obtained in this manner are analysed and the air quality is graded as good, moderate, unhealthy and hazardous. If the air quality is poor, appropriate pollution warnings are given to the general public over radio and television. People in developed countries are educated to take these warnings seriously and take appropriate action. For example, if the suphur dioxide and PM10 levels are high, then asthmatics and those with heart problems are advised to stay indoors. Even healthy people are advised to refrain from jogging and physical exercise.

While failure to take action on air pollution adversely affects the health of people, it also costs the Government millions of rupees for the treatment of affected people in hospitals. A sick population is a major impediment to the development of a country owing to lost national productivity, absenteeism from work places and the drain on health service expenses. Hence it is essential that the Government takes action on air pollution as a matter of highest priority.

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