Why Indoor Air Quality Matters To Your Health – Part I
Introduction to the WHO report on environmental health risks
Environmental risks to global health are well known. According to a WHO report, Preventing Disease Through Healthy Environments, 23% of deaths in 2012 had an environmental cause. Air pollution ranks as the world’s largest environmental health risk causing 7 million deaths per year.
Socioeconomic factors have a strong bearing on the statistics. Poorer countries have a higher proportion of disease burden and mortality attributable to the environment, as high as 31%. With developed countries, this percentage is between 9% and 14%. As an example, low-income countries have as much as a 50% higher proportion of damp housing due to rampant poverty. Poor housing conditions lead to elevated levels of moulds, bacteria and mycotoxins. These microbes can all cause lower respiratory illness in occupants.
Men are more affected by environment-attributed disease than women. This is because more men are exposed through their occupational workplace. The age groups most prone to environment-attributed disease are children under five, and adults between 50 and 75.
Health effects of air pollution and what size particles are we talking about?
What do we mean when we talk about deaths and diseases that are attributable to the environment? Simply put, we are referring to all morbidity caused by external environmental risk factors. These are manifest and diverse. WHO defines environmental risk as the sum of all external agents which can be modified to remove their risk to health. They are thus preventable risks. Excluded are natural environment risk factors, as these cannot be easily modified.
With regard to indoor air quality, there are many environmental risk factors linked to disease. For one, homes located near major roads are prone to receive hazardous levels of diesel fumes from heavy traffic. Particulate matter from this traffic exhaust can lead to a range of lower respiratory illnesses. These particulates are referred to by their size and there is a measure called the particulate matter, or PM class that is used to classify their settling velocity. For example, larger particles >10um are relatively easily filtered out by the nose and upper airway system. Those smaller sized particles, between 2.5 and <10um easily reach the respiratory system causing irritation, while the very small sized particles, those <2.5um reach the alveoli of the lung. Even smaller, nanoscale particulates may enter the blood circulatory system directly and reach the heart and brain.
The most common environmental risk factor is cigarette smoking, both active and passive. Passive or second hand smoke has been attributed to 23% of stillbirths in non-smoking women. Poor foetal development has been linked to exposure to high levels of tobacco smoke and traffic exhaust fumes. There is also an increased risk of child mortality and chronic diseases in later life. 40% of children suffer the effects of tobacco smoke, and long term exposure can exacerbate asthma.
Sufferers of Chronic Obstructive Pulmonary Disease (COPD) experience progressive loss of lung function. Active smoking is the biggest risk factor, together with household air pollution. 35% of 32 million cases of COPD in DALYS are attributable to the environment. DALYS stands for disability-adjusted life years. It is a measure determining days lost through both death and disability.
More common in low-income countries is exposure to particulate matter caused by solid fuel cooking and heating. Half the world’s population cooks with coal or biomass, mostly in the poorer rural areas. If there is insufficient ventilation the smoke will linger inside the home. Finer smoke particles can enter deep into the lungs. This can cause serious respiratory illnesses and decreased lung function in later life.
The particulate matter found in tobacco and cook stove smoke can also lead to ischaemic heart disease (IHD). Accounting for 13% of all deaths, IHD is the leading global killer. In terms of DALYS, 31% of 119 million cases of cardiovascular disease are caused by environmental risk factors such as air pollution.
Contaminants of biological origin
Household dust mites (HDM) are a ubiquitous allergen in homes, which can trigger asthma attacks. The British Thoracic Society doesn’t recommend trying to reduce HDM levels by chemical means. Instead a clean air policy is best. Opening windows to purge the air and regular HEPA vacuuming will help lower HDM levels.
Other hazardous dusts, such as silica and wood dusts, are usually an occupational workplace problem. House renovations and improvements can produce a lot of dust, and workers are recommended to wear a suitable respirator or dust mask. In other cases, the age and condition of the interior have an impact on health. For example, bathrooms that are prone to condensation or have faulty extractor fans can cause a build-up of moisture or condensation conditions that favour mould growth. In other situations, the age of the dwelling or the time since the last renovation can lead to dilapidation causing unexpected water ingress or moisture retention indoors.
Housing which has become damp, perhaps as a result of flooding or from a storm, are prone to much higher levels of mould and bacteria. Some mould is present in all buildings, but if the concentrations are too high, occupants are at risk of lower respiratory illness. Between 5 and 20% of homes have high levels of mould and dampness, contributing to 21% of U.S. child asthma cases. In fact, a 2007 study examined the national annual cost of asthma due to dampness and mould in the USA and calculated the costs at between $2.1 and 4.8 billion per annum. This was linked to at least 4.6 million cases of asthma due to exposure to dampness and mould.
While asthma is largely inherited, environmental factors can exacerbate it. Asthma attacks are caused by either allergenic or non-allergenic triggers. The former include house dust mites, indoor mould and dampness. 44% of 11 million asthma cases in DALYs are triggered by environmental risk factors.
Viral infections are defined as non-allergenic triggers. They cause over 80% of asthma symptoms in children, but that’s not all. 18% of children contract pneumonia through exposure to viruses and bacteria. Viral infections account for over 935,000 deaths a year through respiratory illness, such as bronchitis and pneumonia. Together, household and ambient air pollution accounts for 35% of 52 million lower respiratory infections in DALYS.
Many non-communicable diseases, including cancer and heart disease, have an environmental cause. It’s well known that active tobacco smoking is the biggest single risk factor in developing lung cancer. Less well known is the fact that ambient and household air pollution can cause lung cancer too.
Occupational exposure to organic chemicals, such as benzene and formaldehyde, has been linked to cancer. According to WHO, workers in industries like rubber or petroleum refining are particularly at risk. Many carcinogenic chemicals are found in common household detergents and cleaning sprays. 20% of 49 million cases of cancer in DALYS are down to environmental factors, including air pollution and chemical exposure. A recent 2017 paper evaluated the socio-economic costs of indoor air pollution for selected pollutants at €20 billion euro with 75% of the total caused by particles in the air.
There are other diseases which can arise from occupational exposure. Industrial fumes, for example from metal smelting, can lead to COPD in later life. Occupational exposure to pesticide production has been linked to Parkinson’s Disease.
While more evidence is needed, cleaning sprays, air fresheners and paint all contribute to poor indoor air quality. Prime offenders are the volatile organic compounds (VOCs) contained within, which can trigger asthma attacks. VOCs, such as formaldehyde, are found all kinds of household cleaning materials. Even water-based household paint contains low levels of VOCs, which can take weeks or months to disperse while drying. Furniture and building materials also release VOCs into the air.
Usually indoor air quality is several times worse than the air outside. The best way to reduce the levels of particulate matter and other allergens in the home is by:
• regular HEPA vacuuming,
• using microfiber cleaning cloths and
• adopting a clean air policy.
Part II of this blog article series will focus on indoor air filters. Just taking a few simple steps to lower the levels of dust, mould, smoke and other particulate matter in your home will lead to greater health and wellbeing for you and your family.
Pruss-Ustun, A., Wolf, J., Corvalan, C., Bos, R. and Neira, M. (2016). Preventing disease through healthy environments: a global assessment of the burden of disease from environmental risks. World Health Organization. Sources: http://apps.who.int/iris/bitstream10665/204585/1/9789241565196_eng.pdf
Gautier, C. and Charpin, D. 2017). Environmental triggers and avoidance in the management of asthma. Journal of Asthma and Allergy. 10: 47-56. DOI: 10.2147/JAA.S121276
Peden, D. and Reed, C.E. Environmental and occupational allergies. The Journal of Allergy and Clinical Immunology. 125(2)(Suppl.2): S150-S160. DOI: 10.1016/j.jaci.2009.10.073
Boulanger, G., Bayeux, T., Mandin, C., Kirchner, S., Vergriette, B., Pernelet-Joly, V. and Kopp, P. (2017). Socio-economic costs of indoor air pollution: A tentative estimation for some pollutants of health interest in France. Environment International. 104: 14-24. DOI: doi.org/10.1016/j.envint.2017.03.025
Mudarri, D. and Fisk, W.J. (2007). Public health and economic impact of dampness and mold. Indoor Air. 17: 226-235. DOI: doi:10.1111/j.1600-0668.2007.00474.x