Human society has reached a critical threshold in its relation to its environment. In modern times, several environmental problems pose serious challenges and threats to mankind. Pollution is prominent among them. It is ubiquitous and deep. With the continual improvement in our quality of life, most of us believe that life today is generally healthier than in the past. Doctors and medical scientists, certainly, tell us that we are truly healthier than we have ever been, arguing that medical science has eradicated many of the killer diseases of the twentieth century and mortality rates have fallen.

What they rarely say is that while medical science has obviously eliminated many of the killer diseases, they have been replaced by a growing list of new disorders like cancer, asthma, heart diseases, allergies, chemical poisoning, infertility etc. ~ often less obvious but no less dangerous. What is striking about modern society is not how healthy it is, but how unhealthy.

With the rapid development of economies and booming population growth, various kinds of pollution ~ given as the presence of a wrong thing, in wrong place, in wrong quantity, and at wrong time ~ have been produced. Among various pollution problems, air pollution has caused major concern over the world due to its widespread nature, damage to our environment and potential health risk to humans. A study, conducted jointly by a team of scientists from different institutions spread across India, estimated the impacts of exposure to air pollution and established that about 1.24 million deaths in 2017 were attributable to air pollution. Of these, about 52.4 per cent were of persons aged less than 70 years; the average life expectancy would have been higher by 1.7 years had the air pollution levels been less than the minimum level. No matter where we are, we are always at risk of exposure to airborne pollutants from both indoor and outdoor sources.

Numerous studies in physics, chemistry, geography, and other relevant areas have been conducted to investigate the cause of seriousness of the air pollution problems. Simultaneously, the issue of indoor air pollution also piqued the interest of many scientists, as people spend most of their times (>80 per cent) indoors. Although the time people spend indoors varies with season, age, gender, type of work, health conditions, and so on, good air quality can safeguard the health of occupants and increase the productivity of workers. Generally, indoor air quality is expected to be better than outdoor air quality due to shielding effects of buildings and possible installation of ventilation and air cleaning devices. But in combined indoor and outdoor air quality studies, more than 2/3rds have found indoor air pollutant concentrations higher than outdoor. Many studies have also indicated that indoor air quality is highly affected by the outdoor air quality.

Indoor pollution is a grave and dangerous problem. According to the Global Burden of Disease Study, indoor pollution is a major contributor to ill-health and premature mortality rates in India. According to Dr Srinath Reddy of Public Health Foundation of India: “About 280 crore people are exposed to indoor pollution across the globe of which 78 crore people are in India.” About 4.3 million people die from exposure to household air pollution annually according to World Health Organisation (WHO). A number of air pollutants ~ organic, inorganic, biological or even radioactive ~ have been recognised to exist indoors, including NOx, SO2, O3, CO, volatile and semi volatile organic compounds (VOCs), PM, radon, and microorganisms. Some of these pollutants such as Nox, SO2, O3, PM are common to both indoor and outdoor environments, and some may have originated outdoors. Ill effects of these pollutants depends upon on the toxicity, concentration and exposure time of pollutants, and may vary from person to person.

The common effect is called sick building syndrome (SBS), in which people experience uncomfortable or acute health effects such as irritation in eyes, nose or throat, skin allergies, and so on. The cause of SBS is yet to be known, but the syndrome may disappear once the person affected by SBS leaves the room or the building. SBS can be reduced appreciably by improving ventilation rate of the room.

From cleaning agents used at home to perfumes sprayed on pets, everything leads to indoor pollution at homes. However, a few most common indoor pollutants, their sources and the health hazards they lead to are mentioned here.

One of the best known persistent volatile organic compounds (VOCs) found in the home is formaldehyde. It is a gas that comes mainly from carpets, latex paints, fabric and cheap furniture. Inhalation of formaldehyde causes flu-like symptoms, rashes, neurological illnesses and ultimately cancer. Sources of many other VOCs are solvents and chemicals in perfumes, hair sprays, furniture polish, glues, air fresheners, moth repellents and wood preservatives. Hazardous effects include irritation of eyes, nose and throat. In more severe cases there may be headaches, nausea and loss of coordination. In the long term, some of the pollutants are also suspected to damage the liver and other organs.

In addition, people sometimes apply inappropriate pesticides directly to indoor surfaces, unaware that they are causing their own high exposures. Pesticides that break down within days outdoor may last for years in carpets, where they are protected from the degradation caused by sunlight and bacteria. Carpets are most troublesome because they act as deep reservoirs of toxic compounds.

For many years, the treatment for lice and mites has involved a healthy dose of toxic pesticides. Three types of pesticides used in the preparations are organophosphates, carbamate and pyrethroid. All are neurotoxins, which have also been shown to interfere with the functioning of the immune system. They can also cause endocrine disruption which may not become apparent until a child is older. Some lice shampoo also contains lindane, which when inhaled, ingested or absorbed through the skin, causes vomiting and diarrhea. Carbaryl and pyrethroids are considered to be potential carcinogens.The most dangerous chemicals included in personal care products are ammonia derivatives, such as diethanolamine, triethanolamine, and monoethanolamine. Known to have hormone-disrupting effects, they are added to soaps, bubble baths and facial cleaners. When they are mixed with products containing nitrates, carcinogenic nitrosamines can be formed.

Many chemicals found in common perfumes and fragrances are designated as ‘hazardous’, including methylene chloride, toluene, methyl ethyl ketone, toluene, methyl ethyl ketone, methyl isopropyl ketone, ethyl alcohol and benzyl chloride. Many can cause cancers, birth defects, CNS disorders and allergic conditions. Some doctors believe that perfumes are as damaging to health as tobacco smoke. Environmental tobacco smoke (ETS), including secondhand smoke, causes respiratory irritation, bronchitis and pneumonia in children, emphysema, lung cancer and heart diseases.

Biological pollutants like mites, dust, fungi, parasites are mostly allergens that can cause asthma, hay fever, and other allergic diseases. Tobacco smoke, heaters, gas stoves and furnaces are the sources of carbon monoxide (CO) and nitrogen dioxide. Among other things, CO attacks bloodstream and the central nervous system. Exposure to lowlevel doses of CO can cause nausea, dizziness, headache, ingestion etc. and even be fatal.

There is substantial data available in India, and globally, about the health consequences for women and children due to indoor pollution caused by solid fuel use in households. Household air pollution caused by combustion solid fuel, mainly in chulhas, is responsible for 1.04 million premature deaths and 31.4 million lost life years annually in India which is much higher than premature deaths and lost life years due to outdoor air pollution.

In India, an estimated four lakh deaths from acute lower respiratory infection (ALRI) in children younger than five and 34,000 deaths from chronic obstructive pulmonary disease (COPD) in women are attributed annually to household solid fuel use. Globally, exposure to indoor smoke from solid flues is responsible for over half of the 1.8 million annual deaths from acute lower respiratory infections, making it a largest environmental factor causing ill health and deaths among children

Many studies indicate that indoor air quality is affected by outdoor air. There are three main mechanisms that allow outdoor air to enter indoor environment: mechanical ventilation, natural ventilation and infiltration. However, good indoor air quality is critically important to safeguarding our health since we spend most of our time indoors. As the overall indoor air quality depends on the contribution of both the indoor and outdoor environments, measures and strategy to control indoor air pollution should be formulated. While regulations have improved the quality of outdoor air, problems that persist indoors have received too little attention.We may quote one sentence from the VIth report of the Royal Commission on Environmental Pollution: ‘Our concern is not that pollution is not always given top priority, it is that it is often dealt with inadequately and sometimes forgotten in the planning process.’

The writer is a retired IAS officer