Air Quality And Height: Are Higher Floors Healthier?

Air pollution is a serious issue, with only 1% of China's 500 largest cities meeting the air quality standards set by the World Health Organization. A common belief is that living on higher floors can help mitigate the effects of air pollution. This belief has some merit, as residents on lower floors are often exposed to high levels of exhaust from street-level traffic and parking garages. However, the relationship between floor level and air quality is complex and influenced by various factors such as building type, season, and geographic location. While higher floors may have slightly lower levels of large particle pollutants, small particle pollutants like PM2.5 can still reach high floors and pose health risks.

Air pollution and health risks

Air pollution is a significant issue in many cities worldwide, and it can pose various health risks to residents. The impact of air pollution on health can vary depending on several factors, including the floor level of one's residence in a high-rise building.

Several studies have investigated the relationship between floor level and air quality, particularly in high-rise buildings. Some research suggests that individuals living on higher floors may experience better air quality due to reduced exposure to street-level traffic exhaust and parking garage emissions. This advantage may be more pronounced in buildings set back from the street and surrounded by open green spaces. Additionally, higher floors may have slightly fewer large air particles.

However, it is important to note that the presence of inversion layers, which are a significant contributor to air pollution, can worsen air quality on higher floors. During certain weather conditions, such as in the daytime when air mixes to higher altitudes, the air pollution levels on higher floors may be comparable to or even worse than those on lower floors.

The health risks associated with air pollution are well-documented. Poor air quality, particularly from smog and particulate matter (PM2.5), can increase the risk of respiratory and cardiovascular problems, including lung cancer and cardiac arrest. In certain geographic areas, ground-floor residents may be exposed to natural radon gas, which can also lead to lung cancer. Additionally, the survival rates during a cardiac arrest emergency have been found to be lower for residents on higher floors due to longer response times for first responders.

While the evidence suggests that floor level can influence air quality and, consequently, health outcomes, it is essential to consider other factors as well. Socio-economic factors, for instance, may play a more significant role in certain regions, where living on a higher floor is associated with higher prestige and access to better healthcare and resources.

Air quality and survival rates

Air pollution is a serious issue that affects people worldwide, and it is linked to survival rates in several ways. Firstly, air pollution is a significant contributor to premature deaths, with an estimated 4.2 million deaths attributed to ambient (outdoor) air pollution and 6.7 million deaths linked to the combined effects of ambient and household air pollution in 2019. The World Health Organization (WHO) estimates that 68% of these premature deaths were due to ischaemic heart disease and stroke, 14% to chronic obstructive pulmonary disease, 14% to acute lower respiratory infections, and 4% to lung cancers. These health risks are particularly prevalent in low- and middle-income countries, with 89% of premature deaths occurring in these regions.

The impact of air pollution on survival rates is further evident when examining life expectancy. In 2019, air pollution reduced average life expectancy by one year and eight months worldwide. This impact is comparable to the reduction in life expectancy caused by tobacco use. Less-developed and low-income countries are disproportionately affected, with the greatest losses in life expectancy attributed to air pollution observed in Oceania, South Asia, and sub-Saharan Africa. These regions can experience reductions in life expectancy of up to 2.8 years due to air pollution.

To improve survival rates and mitigate the health risks associated with air pollution, individuals can take protective measures such as "sheltering in place" during periods of poor air quality. This involves staying indoors, closing windows and doors, and sealing the home to prevent exposure to outdoor pollutants. Additionally, seeking higher ground or floors in buildings may offer some respite from large particulate matter, although it is less effective against smaller PM2.5 particles, which can reach significant heights and affect air quality even on elevated floors.

While individual actions can provide some protection, addressing air pollution and improving survival rates on a broader scale requires collective efforts and policy interventions. The WHO provides global guidance through its Air Quality and Health Unit, which works across knowledge, evidence, capacity building, and coordination to support member states in implementing effective policies. These policies include promoting cleaner transport, energy-efficient homes, improved power generation and industrial practices, and better municipal waste management to reduce key sources of outdoor air pollution. By implementing and enforcing such policies, countries can significantly improve air quality, reduce health risks, and positively impact the survival rates of their populations.

Floor level and airborne-pollutant levels

While there are no inherent health risks associated with living in a high-rise building, several factors, including air quality, may affect the health of high-rise dwellers. A study conducted in New York City analysed the relationship between floor level and traffic-related airborne-pollutant levels. The study categorised floor levels into three groups: 0–2nd, 3rd–5th, and 6th–32nd. It was found that outdoor airborne-pollutant levels were highest at the 3rd–5th floors, while indoor Σ8PAHsemivolatile levels were significantly lower at the 0–2nd floors compared to higher floors. Additionally, indoor Σ8PAHnonvolatile levels showed a decreasing trend with increasing floor levels.

Another study in Beijing measured PM2.5 levels from the 1st to the 22nd floor of an apartment building on two polluted summer days. The results showed that PM2.5 levels decreased with increasing floor level, with lower readings on the second day, which was less polluted than the first. However, it is important to note that the measurements were taken at hallway windows, which may not accurately represent the pollution levels inside residences.

The impact of floor level on airborne-pollutant levels can also vary depending on the season. For example, during the non-heating season, outdoor and indoor BC (black carbon) concentrations at the 6th–32nd floors were significantly lower than at lower floors. On the other hand, during the heating season, indoor Σ8PAHnonvolatile levels tended to increase with higher floor levels.

In certain geographic areas, ground-floor residents may be exposed to natural radon gas seeping up from the ground, which can pose health risks such as lung cancer. Additionally, living on higher floors can have other health implications, such as decreased chances of surviving a cardiac arrest due to longer response times for first responders.

Building type and air pollution

People tend to spend most of their time indoors, with research showing that adults in North America spend 87% of their time in buildings. Therefore, indoor air quality (IAQ) is crucial to human health and productivity.

The World Health Organization (WHO) has recognised indoor air pollution as a multi-disciplinary phenomenon, classifying pollutants into several categories. According to the WHO, in the year 2000, over 1.5 million deaths were caused by indoor air pollution.

Indoor air pollution is influenced by various factors, including inadequate ventilation, the use of air conditioning systems, human activities, and the presence of different materials, chemicals, and gases. Outdoor air pollution can also impact indoor air quality, especially in buildings with limited ventilation systems.

The type of building and its purpose play a significant role in determining indoor air quality. For example, residential buildings and commercial structures have different construction methods and materials, which can affect the types and levels of pollutants present. Energy-saving measures, such as improved insulation and airtightness, can reduce the circulation of fresh air, impacting IAQ.

Additionally, the use of synthetic materials, chemicals, and pesticides in indoor environments can contribute to indoor air pollution. Cooking appliances, heating systems, and hot water heaters that burn fuel can also release pollutants and contribute to ground-level ozone and fine particle pollution.

To improve indoor air quality and reduce pollution, it is essential to transition to cleaner sources of energy, such as renewable, non-combustion energy from the sun, wind, and water. Promoting sustainable and non-toxic building materials, improving ventilation strategies, and designing buildings for their specific climate can also help mitigate indoor air pollution.

While the height of a building may have some impact on air pollution levels, with higher floors potentially having slightly fewer large particles, the focus on building type and air pollution should primarily be on the indoor environment and the factors that influence it.

Air circulation and light in high-rise buildings

Air circulation and natural light are important considerations when designing high-rise buildings to ensure the comfort and health of their occupants.

High-rise buildings can utilise natural ventilation through a design feature called a light well or deep courtyard, which admits daylight and natural airflow. Light wells in the centres of high-rise buildings in Japan are called 'Voids'. Voids are vertical hollow cores that improve ventilation and thermal comfort. Outdoor air flows through passageways and is discharged into the Void, creating a natural ventilation flow. Gas water heaters built into Voids must have a large enough opening at the bottom to maintain acceptable indoor air quality (IAQ) by preventing the contamination of exhaust gases.

Computational Fluid Dynamics (CFD) simulations have been used to model airflow inside light wells, and various numerical turbulence models have been employed to predict natural ventilation rates. These models take into account factors such as wind force, thermal buoyancy, and heat sources like water heaters to ensure accurate predictions of vertical temperature distribution and ventilation rates.

In addition to natural ventilation, mechanical systems also play a role in air circulation in high-rise buildings. The stack effect, for example, can cause problems with ventilation in high-rise buildings during winter. Pressure differences at elevator doors have been studied to understand their impact on the ventilation behaviour of the entire building. It was found that the opening and closing of entrance and elevator doors can significantly influence pressure differences and, consequently, the ventilation performance of the building.

While higher floors in high-rise buildings may offer a sense of isolation from the surrounding environment, the impact on air pollution levels, particularly PM2.5 particles, is less clear. Tests conducted in an apartment building in Beijing showed that PM2.5 levels on higher floors were still above the World Health Organization's 24-hour limit, indicating that simply residing on a higher floor may not be sufficient to escape air pollution. However, air mixing heights vary during the day and night, and in different seasons, so the impact on air pollution levels in high-rise buildings can be complex and dependent on various factors.

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