International guidelines and indoor air quality standards
In various other posts on our blog, we’ve highlighted the importance of monitoring and improving indoor air quality (IAQ). But against what standard do you benchmark recorded IAQ levels? And to what gold standard do you aspire when cleaning the air up?
Indoor air quality standards form the bedrock upon which all our air quality management activities must be built. But while there are several guidelines and recommendations to measure and clean up indoor air, there aren’t very many standards. This isn’t necessarily a matter of apathy about clean air; there are standards for what constitutes healthy air outdoors. But be it for outdoor air or indoor air, forming a uniform standard for large regions is undoubtedly tricky. This is because pollutants, technological feasibility, infrastructure, and culture vary from region to region, city to city, and sometimes even home to home.
In the next few blog posts, we will examine the ABCs of IAQ guidelines. We’ll examine how national governments can adapt these guidelines to establish indoor air quality standards for office buildings and residential buildings. And we’ll explore existing frameworks and indoor air quality standards in India, especially as compared to the USA.
What are air quality standards?
Air quality standards are distinct from air quality guidelines.
Air quality standards define the acceptable level of air pollution in indoor, outdoor, or both environments in a particular country or region. They usually define the level of specific pollutants over a particular averaging time. For instance, they set the maximum permissible concentration of particulate matter (PM) in a region over a 24-hour period. Such standards are outlined and adopted by regulatory authorities or industry bodies. While they specify acceptable air quality levels, they may or may not be legally binding.
Guidelines, on the other hand, are mere suggestions. While they educate home and business owners about the IAQ levels they should maintain, their enforcement is not monitored or regulated. Further, they lack certain elements or details that make standards precisely measurable and, hence, enforceable.
According to the World Health Organisation (WHO), ambient and indoor air quality standards will usually specify the averaging time, the measurement technique and strategy, data handling procedures, and the statistics used for measurement and comparison. Additionally, a standard may permit a specified number of times that it can be broken up to a certain limit in a given period.
As we mentioned earlier, it isn’t easy to set standards for air quality, especially indoors. This is because of the sheer range of variables involved in not only air pollution but also air quality management. The WHO notes that air quality standards could be based only on scientific evidence and public health considerations. Or they may also take into consideration enforcement potential, the cost-benefit ratio of air cleaning, the technological feasibility of achieving the defined standards, or the existing infrastructural, social, cultural, and economic circumstances that might influence their adoption.
Phew. That’s a lot of things to consider, and that list isn’t even exhaustive. Given the complexity of the matter, authorities may set multiple standards to achieve different short- and long-term goals. Additionally, these standards need not be set in stone over the long term. Ideally, they should be reviewed periodically to evolve with newly emerging risk factors and/or scientific evidence.
Going from guidelines to standards
Indoor air quality standards are largely implicit. They are based on guidelines created by the WHO, the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), the USA’s Occupational Safety and Health Administration (OSHA), the US Centres for Disease Control and Prevention (US CDC), and/or other public, occupational, and environmental health bodies.
Let’s take the WHO, for example. As the United Nations’ designated global health agency, the WHO has published global air quality guidelines for PM, ozone, nitrogen dioxide, sulphur dioxide, and carbon monoxide. The agency has also published indoor air quality guidelines focusing on pollutants like benzene, carbon monoxide, formaldehyde, radon, and naphthalene in enclosed environments.
The purpose of publishing these guidelines? To identify the optimal level of air quality and provide a uniform, scientifically-informed basis to protect public health from the impacts of air pollution in different contexts. Essentially, they offer a pathway for countries to transform recommended air quality levels into legally enforceable standards.
Naturally, even as countries use the WHO’s air quality guidelines as a starting point, their air quality standards must fit within their own legal frameworks. They must consider emission sources specific to their country. And they must take into account features of the population and the environment.
In general, a comprehensive and targeted air quality standard must consider:
- Which pollutants should be regulated – this also includes numerical values for specific pollutant concentrations and appropriate detection and monitoring techniques
- The air pollution-linked health effects which need to be addressed – this includes consideration of the demographic groups most at risk from air pollutants
- Permissible risk levels – this covers the potential economic and health costs that are acceptable to the population
- The feasibility of compliance – this includes assessing the costs of compliance vs the benefits earned
- And the feasibility of enforcement – while more detailed than guidelines, standards may or may not be legally binding. If they are legally binding, national governments must identify authorities who will oversee their enforcement.
The microenvironmental model
From homes, public transit, streets, and parks to workplaces, schools and beyond, individuals move through several environments in a day. How can air quality guidelines and standards assess people’s exposure to and risk from air pollutants? As people encounter different environments, they are exposed to different pollutants, with exposure being either acute or chronic. How, then, can risk be effectively assessed and addressed?
Enter the microenvironmental model. A microenvironment is a place where people spend time and which has a specific pollutant profile for the time duration that people occupy it. The microenvironmental model is a comprehensive construct to assess exposure to inhaled pollutants and their associated risks. Every place from the inside of a motor vehicle, a kitchen, the printing room in your office to a crowded street at peak traffic time constitutes a microenvironment.
When estimating personal exposure and setting indoor air quality standards, this microenvironmental model is particularly important. For instance, even if you spend only 15 minutes cooking in the kitchen per day, if the space is not well-ventilated, you risk acute exposure to air pollutants, the nature of which will be determined by the type of cooking fuel you use.
Since we spend large amounts of time indoors – at work and at home – it is vital to set indoor air quality standards for office buildings and residences. Assessing exposure in such microenvironments should account for not only pollutants with indoor sources but also the indoor penetration of outdoor air pollutants.
As you can see, the microenvironmental model is highly relevant to our concern of indoor air quality standards. Indoor microenvironments must be monitored for air quality for several reasons. One, to prevent airborne disease transmission (as the Covid pandemic made evident). Two, to promote building efficiency, which is, to a large extent, a function of HVAC system efficiency. And three, to enhance occupant health and well-being – clean air not only improves comfort and cognition but also minimises exposure to allergens and other substances that can cause respiratory distress and other health issues.
Going ahead, we’re going to take a look at specific indoor air quality standards in India and in the USA, for residential and commercial spaces. Whether you’re an HVAC specialist, a public health professional, or involved in the design, construction, or use of buildings in any way, the following articles will definitely offer some useful information for you.
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