Air Pollutants: Measuring The Major Contaminants

Air quality is measured using the Air Quality Index (AQI), which works like a thermometer that runs from 0 to 500. The AQI tracks five major air pollutants: ground-level ozone, airborne particles, carbon monoxide, nitrogen oxides, and sulfur oxides. These particles are monitored by instruments on the ground and satellites orbiting the Earth, such as the Joint Polar Satellite System (JPSS). The AQI value indicates the level of health concern, with values at or below 100 generally considered satisfactory, and values above 100 indicating unhealthy air quality.

Measuring particulate matter (PM)

Particulate Matter (PM) is a serious environmental pollutant linked to a variety of adverse health effects. It refers to a number of tiny particles that float around in the air and affect many things, including health and the environment. Particulate matter is not a single substance but is made up of a variety of different substances. This means that there are also multiple sources of PM.

PM is measured using a number of methods, including Federal Reference Methods (FRMs), Federal Equivalent Methods (FEMs), and low-cost sensors. FRMs are the gold standard for measuring PM and many other air pollutants. They typically employ gravimetric methods to measure particulate matter. This involves intaking air to collect particles on filters, which are then weighed and analysed in a lab. The actual mass concentration values are generated by "measuring a filter's weight before and after sample collection and then dividing the difference by the total volume of air sampled through the filter".

FEMs are similar to FRMs but are not standardised. This means that many different methods and pieces of hardware can be used in a Federal Equivalent Method. One of the more commonly used FEMs is a Beta Attenuation Monitor (BAM). BAMs use "beta-ray attenuation to measure the mass concentration of PM in ambient air". This involves sending beta particles through a piece of filter tape that collects particulate matter in the air. The "difference in the degree of attenuation between the pre-and-post-sampled filter tape is directly proportional to the mass of PM in the sampled air".

Low-cost sensors are cheaper than FRMs and FEMs but can still run from the low hundreds to thousands of dollars. They are useful for communities that want to know about their air quality and take action to improve it. An example of a low-cost sensor is the PurpleAir monitor, which has been evaluated for use in parks that do not have a particulate monitor.

There are also other methods for measuring PM. For example, air quality monitors are outfitted with sensors designed to detect specific pollutants. Some use lasers to scan particulate matter density in a cubic metre of air, while others rely on satellite imaging to measure energy reflected or emitted by the Earth.

Assessing health impacts of air pollutants

Air pollution is the presence of contaminants in the atmosphere, such as dust, fumes, gases, mist, odour, smoke, or vapour, in quantities and durations that can be harmful to human health. The main pathway of exposure is through the respiratory tract, but some pollutants are small enough to enter the bloodstream through the lungs and circulate throughout the body. These pollutants can cause systemic inflammation and increase the risk of disease.

The health impact of air pollution exposure depends on the duration and concentration of exposure, as well as the health status of the affected populations. Short-term and long-term exposures can both lead to health problems, and the levels of exposure that are considered 'safe' vary by pollutant and disease outcome. Fine particulate matter (PM), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2) are among the pollutants of greatest public health concern.

To assess the health impacts of air pollutants, organisations like the European Environment Agency (EEA) and the US Environmental Protection Agency (EPA) conduct research and produce annual health risk assessments. These assessments use air quality data, information on population and health outcomes, and World Health Organization (WHO) recommendations to estimate the health risks and impacts of air pollution on a population level. The results inform policy development and implementation to improve air quality.

The EPA, for instance, uses the Air Quality Index (AQI) as a yardstick to measure air quality. The AQI runs from 0 to 500, with higher values indicating greater air pollution and health concern. An AQI value of 50 or below represents good air quality, while a value over 300 indicates hazardous air quality. The AQI is divided into six categories, each representing a different level of health concern and assigned a specific colour. This allows communities to quickly determine if the air quality is reaching unhealthy levels.

Research by the EPA and others also informs the review of National Ambient Air Quality Standards (NAAQS). Integrated Science Assessments (ISAs) are conducted to assess the current state of scientific knowledge on criteria air pollutants and determine if the standards adequately protect public health. These assessments consider factors such as proximity to industrial sources of pollution, underlying health issues, nutrition, stress, and other sociodemographic factors that may influence health outcomes in exposed populations.

Identifying sources of air pollution

Mobile sources include vehicles such as cars, buses, planes, trucks, and trains. These sources account for more than half of all air pollution in the United States, with automobiles being the primary contributor, according to the Environmental Protection Agency (EPA).

Stationary sources refer to fixed locations like power plants, oil refineries, industrial facilities, and factories. These sources emit large amounts of pollution and are also known as point sources. Power plants, for example, can increase smog levels in nearby parks.

Area sources are made up of multiple smaller pollution sources that may not be significant on their own but can have a cumulative impact. Examples include agricultural areas, cities, and wood-burning fireplaces.

Natural sources include wind-blown dust, wildfires, and volcanic activity. While these sources can sometimes be significant, they typically do not create ongoing air pollution issues compared to human-generated sources.

To effectively address air pollution, it is essential to target both regulated and unregulated pollutant sources. Regulated sources, such as electricity generation and passenger vehicles, may require more drastic emissions reductions. At the same time, less extensively regulated sources like manure management, personal diets, and the formulations of cleaning supplies, paints, and inks, should also be addressed.

Additionally, it is worth noting that air pollution-related deaths are caused by a combination of direct toxicity and particulate matter. Fine particulate matter, known as PM2.5, is associated with heart attacks, strokes, lung cancer, and other diseases. About half of the deaths related to PM2.5 are attributed to burning fossil fuels, with the rest linked to animal agriculture, dust from construction and roads, and burning wood for heating and cooking.

Climatic factors influencing air pollution

Climatic factors play a significant role in influencing air pollution levels and their impact on human health. Firstly, climate change is expected to worsen harmful ground-level ozone, particularly in areas with hot, sunny days which contribute to the formation of ozone. This can have detrimental effects on human health, as ozone is a major air pollutant that can irritate the respiratory system and lead to respiratory diseases. Climate change can also increase people's exposure to allergens like pollen, affecting individuals with allergies and respiratory issues.

Secondly, alterations in precipitation patterns and humidity levels due to climate change can impact air pollution. Increased humidity and stagnation events can elevate PM2.5 levels, fine particulate matter that poses health risks. Changes in precipitation and atmospheric mixing influence PM2.5 levels, but the net effect is uncertain due to the complex interactions of these factors.

Thirdly, extreme weather events associated with climate change, such as flooding and storm surges, can indirectly contribute to air pollution. These events can cause indoor damp conditions, leading to the growth of harmful pollutants like mold, bacteria, and volatile organic compounds. Indoor air quality is crucial as people spend the majority of their time indoors, and poor indoor air quality has been linked to respiratory diseases, heart disease, and cancer.

Lastly, climate change can increase the frequency and intensity of wildfires, which produce smoke that lowers air quality and harms human health. Wildfire smoke contains polycyclic aromatic hydrocarbons (PAHs), toxic compounds that have been linked to eye and lung irritation, blood and liver issues, and even cancer.

Overall, the impact of climatic factors on air pollution is complex and varies by region. While certain meteorological conditions can exacerbate air pollution, regulatory initiatives, partnership programs, and individual actions can help mitigate these negative effects and improve air quality, protecting human health and the environment.

Strategies to minimise negative impacts

Strategies to minimise the negative impacts of air pollution include a range of approaches, from international agreements to local initiatives. Here are some key strategies:

International Agreements and Policies

The Paris Agreement (2015) is a global effort to combat climate change and limit global warming to below 2°C. This agreement encourages countries to implement policies that reduce greenhouse gas emissions and mitigate the dangerous impacts of climate change. The World Health Organization (WHO) also plays a crucial role in providing evidence-based guidelines and supporting countries in developing policies to protect public health from air pollution.

National and Regional Regulations

Many countries have enacted regulations to control air pollution. For example, the Clean Air Act in the United States, established in 1970, authorises the Environmental Protection Agency (EPA) to regulate harmful air pollutant emissions. The EPA has issued emissions standards for various industries, including chemical plants, oil refineries, and manufacturing facilities, leading to significant reductions in toxic air pollution. The National Emission Reduction Commitments Directive in Europe sets national reduction commitments for several key air pollutants, including nitrogen oxides and fine particulate matter.

Urban Planning and Transport

Urban areas are particularly vulnerable to air pollution. Strategies to minimise pollution in cities include improving waste management practices, such as capturing methane emissions from waste sites, and promoting clean modes of transportation. This can involve prioritising walking, cycling, and rapid urban transit networks, as well as encouraging the use of low-emissions vehicles and fuels. The establishment of subway systems in cities has proven effective in reducing air pollutant concentrations. Additionally, improving the energy efficiency of buildings and incorporating more green spaces can help minimise the negative impacts of air pollution in urban areas.

Control Strategies for Industries

Industries play a significant role in contributing to air pollution. Strategies to minimise their negative impacts include implementing clean technologies to reduce industrial smokestack emissions, improving fuel quality, and adopting alternative fuels and energy sources, such as solar power and natural gas.

Health Impact Assessments and Air Quality Management

Health Impact Assessments (HIAs) and Air Quality Management (AQM) strategies are important tools for minimising the negative health impacts of air pollution. AQM involves setting standards for air quality, designing and implementing control strategies, and regularly assessing progress. HIAs help evaluate the health risks associated with air pollution and guide policy decisions to protect public health.

By implementing these strategies and continuing to prioritise the reduction of air pollutants, societies can effectively minimise the negative impacts of air pollution on human health and the environment.

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