Qualité de l’air à Memphis

Is memphis a polluted city?

Memphis is a city situated on the banks of the Mississippi River in Tennessee. Because of its riverine location, Memphis has the fifth busiest port in the US, receiving cargo from across the world before being forwarded by road transportation across the entire US. Add to this the international airport and it’s easy to understand why Memphis is such a busy multi-modal transportation hub, despite its inland location.

The 2019 population of the metropolitan area was an estimated 1.35 million people.

In early 2021, Memphis was enjoying a period of “Good” quality air with a US AQI reading of 30. This is in accordance with the suggested figures from the World Health Organisation (WHO). The main pollutant was ozone (O₃) with a concentration of 74 µg/m³. With air quality as good as this, doors and windows can be safely opened to enjoy the fresh air. All types of outdoor activity can be enjoyed without fear.

Does the air quality in Memphis vary throughout the year?

Looking back over the records for 2020, it can be seen that for 9 months of the year Memphis achieved the WHO target figure of less than 10 µg/m³. In June, July and August the air quality was classed as being “Good” with readings between 10 and 12 µg/m³. The 2020 average was 8.1 µg/m³.

In 2019, once again, for 9 months of the year Memphis achieved the WHO target figure. In June, the air quality was classed as being “moderate” with readings between 12.1 and 35.4 µg/m³ and the remaining months of May and September saw “Good” air quality with figures between 10 and 12 µg/m³.

When studying the figures from previous years it can be seen that the air quality remains about the same. In 2017 the level was 7.9 µg/m³, 2018 saw the level at 8.1 µg/m³ and in 2019 there was a slight rise to 8.2 µg/m³.

How does Memphis rank in the air pollution stakes?

The American Lung Association’s 2020 “State of the Air” report ranked Memphis as the 43^rd most polluted city in the nation for ozone (O₃) pollution, a decline from last year’s figures. The report studies the two main contributors, which are ozone as well as PM2.5 and PM10.

Ozone pollution and particle pollution are two of the most widespread and dangerous air pollutants. Breathing these pollutants can trigger asthma attacks, heart attacks, coughing, wheezing and can also result in cardiovascular damage and developmental and reproductive harm.

The report showed that almost half of people in the United States (45.8 per cent) which equates to about 150 million Americans, lived in counties that had unhealthy ozone and/or particle pollution in 2016-2018, a significant increase compared to the previous three reports.

Memphis is one of the numerous cities that experienced high numbers of unhealthy days on average for ozone pollution. Compared to the 2019 report, Memphis experienced five more unhealthy days of high ozone in this year’s report. This is being blamed on the overall higher temperatures brought about through climate change.

Where does the air pollution in Memphis come from?

There are four main pollutants that are measured which are ozone (O₃), Particulate Matter (PM2.5 and PM10), carbon monoxide (CO) and sulphur dioxide (SO₂). The two main pollutants in the Mid-South are ozone and Particulate Matter. Ozone production increases due to car exhaust and factory fumes. While particulate matter is mainly caused by dust, ash and smoke.

Weather plays a major role in increasing the pollutants as well, when we have hot, dry weather with calm winds, the air becomes more stagnant, keeping the pollutants near the surface which leads to poor air quality.

Southwest Memphis is a residential region surrounded by fossil fuel burning, steel refining, and food processing industries, and considerable mobile sources whose emissions may pose adverse health risks to local residents.

Is anything being done to improve the air quality in Memphis?

Particle pollution levels have improved recently due to the clean-up of coal-fired power plants and the retirement of old, dirty diesel engines.

When air quality is poor, people are recommended to conserve energy, as power plants can increase the poor air quality. People are also encouraged to carpool or drive less, to help reduce the amount of ozone in the atmosphere. During times such as these, people should be encouraged to walk or cycle or to make full use of the public transportation system.

Air pollution from major factories in Shelby County has declined by more than 50 per cent during the past decade.

Operators of plants that are major sources of "priority" pollutants such as nitrous oxides, sulphur dioxide, carbon monoxide, particulates and volatile organic compounds pay a fee for each ton they discharge, and they also ante up a sum to apply for air-pollution permits.

Some of these reductions were due to the closure of some of the older facilities that could not be easily brought up-to-date with retrofitted technology. A further portion of the reductions can be attributed to the latest raft of air scrubbers, cleaners and filters that have recently been fitted to manufacturing units.

How is human health affected by the poor air quality in Memphis?

Children under the age of 14 years, senior citizens and people with pre-existing medical conditions such as asthma and chronic obstructive pulmonary disease, people with cardiovascular diseases, and people with diabetes are especially vulnerable to air pollution.

In Shelby County, there are currently over 22,000 children and 68,000 adults registered as being asthmatics, 72,000 people with chronic obstructive pulmonary disease (COPD) and 80,000 people with heart disease who face greater risk from poor quality air.

Air pollution is the main environmental risk to public health in North America.

Worldwide, nearly 7 million premature deaths were attributable to ambient air pollution in 2016. About 88 per cent of these deaths occur in low- and middle-income countries.

Ground-level ozone is one of the main components of smog. It is formed by the reaction of sunlight (photochemical) with pollutants such as nitrogen oxides (NO_x) emanating from vehicles or industry, and volatile organic compounds (VOCs) emitted by vehicles, solvents and industry. The highest ozone levels are recorded during periods of sunny weather, especially during the afternoon when the sunlight is at its strongest.

Excess ozone in the air can cause serious adverse effects on human health. It can cause breathing problems, exacerbate asthma, reduce lung function, and lead to lung disease. It is currently one of the atmospheric pollutants of greatest concern.