Qualité de l’air à Las Vegas

What is the current state of air quality in Las Vegas?

Las Vegas is officially known as the City of Las Vegas but often known simply as Vegas, is the 28^th most populous city in the US and the most populous city in the state of Nevada. It also calls itself “The Entertainment Capital of the World”, and is famous for its mega casino-hotels and associated activities. Another name it is often called is “Sin City” because of its tolerance for adult-themed entertainment.

In 2010 the estimated population of the city was almost 600,000 people. This was revised in 2019 which added another 500,000 to it. The population of the entire metropolitan area was 2.25 million people. This ranked it as the 23^rd most populous metro area in the US.

During the early months of 2021, Las Vegas enjoyed a period of “Good” quality air with a US AQI reading of 31. This is in line with the classifications recommended by the World Health Organisation (WHO). The concentrations of the recorded pollutants were, PM2.5 - 1.5 µg/m³ and PM10 - 34.3 µg/m³. With levels as low as these, you should have no reserves when opening doors and windows to let some fresh air inside. All forms of outdoor activity can be enjoyed without fear.

Throughout most of 2020, Las Vegas attained the target figure for air cleanliness as laid down by the WHO. The figure to achieve is 10 µg/m³ or less. It was only during the month of September that the target was missed. A spike in pollution pushed the figure into the “Moderate” classification with figures between 12 and 35.4 µg/m³.

The long-term trends from 2000 to 2019 indicate subtle improvements in Las Vegas ozone and annual PM2.5 averages. Progress has not been a straight line, however, as numerous years have shown an increase in pollution levels.

Understanding the full picture is more complex than simply analysing Las Vegas AQI for annual average pollution levels. While average pollution levels in the last three years have shown improvements, Las Vegas’s number of days qualifying as “unhealthy” for PM2.5 and ozone has been on the rise since 2016.

For the 12-year period from 2004 to 2016, Clark County met daily attainment levels for PM2.5. Only in recent years have daily PM2.5 levels increased to result in the city no longer attaining prescribed levels. These increases come despite improving average annual PM2.5 levels.

Ozone has also increased in recent years, from a weighted average of 20.3 unhealthy days from 2014 to 2016 to 30.2 unhealthy days from 2016 to 2018. Complicating the problem of reaching ozone attainment, the US Environmental Protection Agency (EPA) implemented a more stringent ozone standard of 70 ppb (as opposed to the previous requirement of 75 ppb) in 2015.¹ Since ozone is not emitted directly, but rather formed in the atmosphere from other pollutants, it can be more difficult to control, especially against rising temperatures that have resulted from climate change. Transportation emissions, which emit the majority of precursor pollutants, should be targeted.

Cleaner, more fuel-efficient and low-emission vehicles offer an opportunity to drive Las Vegas’s pollution levels down further. Currently, only 1 to 2 per cent of vehicles sold in Nevada is electric.² Governor Steve Sisolak moved to implement more stringent auto emission standards following a precedent set by California, setting new exhaust emission standards effective as of 2024 and requiring car dealers to sell a certain percentage of zero-emission vehicles. The plan has been devised to specifically help tackle Las Vegas’s worsening air quality problem.

Does the air quality in Las Vegas differ throughout the year?

Looking back at figures released on the IQAir website it can be seen that for 11 months of the year in 2020, Las Vegas achieved the World Health Organisation’s target figure of less than 10 µg/m³. Only during the month of September did the figure rise to 13.5 µg/m³, which classified the quality as being “Moderate”.

Historically, the air quality does not change much, either for the better or the worse. In 2017, an annual average figure was recorded as being 7.5 µg/m³ and the following year it returned a reading of 7.2 µg/m³. A slightly better figure from 2019 at 6 µg/m³ and an average of 7.2 µg/m³ from 2020.

What is the source of air pollution in Las Vegas?

Air pollutants are emitted from a range of both man-made and natural sources including:

• burning of fossil fuels in electricity generation, transport, industry and households;
• industrial processes and solvent use, for example in the chemical and mining industries; agriculture, from fertilisers and from emissions from livestock;
• waste treatment;
• natural sources, including volcanic eruptions, windblown dust, sea-salt spray and emissions of volatile organic compounds from plants.

Air pollutants can be released directly into the atmosphere (primary emissions) or can form as a result of chemical interaction involving precursor substances, which requires ultraviolet light. The air pollutant emissions cause air pollution, however, reductions in emissions do not always automatically result in significant cuts in concentrations. There are intricate links between air pollutant emissions and air quality. These include emission heights, chemical transformations, reactions to sunlight, additional natural contributions and the impact of weather and topography. Significant cuts in emissions are essential for improving air quality.

Around 90 per cent of ammonia emissions and 80 per cent of methane comes from agricultural activities. Energy production and distribution account for around 60 per cent of sulphur oxides.

More than 40 per cent of PM2.5 pollutants come from transport and 40 per cent of nitrogen oxides also come from transport.

High temperatures, minimal precipitation, and a fast-growing population set the backdrop to Las Vegas’s unhealthy air quality. Transportation, construction, and industrial emissions, meanwhile, are the direct culprits for emitting harmful levels of PM2.5 and ozone precursor pollutants into Las Vegas' air. Together, these effects combine to create ideal circumstances for ozone formation and prevalent PM2.5 as well as challenges to clearing the skies with precipitation and wind.

Las Vegas is the most populated city in Nevada and has experienced considerable growth since the 1990s. Between 1990 and 2000, the population increased by 85 per cent, nearly doubling in size.³ The city’s status as the Entertainment Capital of the World brings in tourists from near and far: Las Vegas frequently ranks among the most visited tourist destinations in the world. With a booming population and tourism industry, Las Vegas is significantly impacted by transport emissions and construction activity.

Normally, pollution is dispersed into the atmosphere or tamped down by weather effects, such as rain and wind. Rainfall in Las Vegas, however, is scarce. On average, Las Vegas gets 4.2 inches of rainfall dispersed over 21 rainy days.⁴ As a result, pollution removal from rain (especially particulate matter) is rare. Las Vegas’s winter experiences very mild winds and a weather phenomenon referred to as a temperature inversion, which traps pollution near the ground. As a result of these weather effects, Las Vegas’s most polluted months are in the winter. In 2018 and 2019, December, January and November were respectively the city’s most polluted.

Lower-income neighbourhoods, such as those near the airport, power plants, and major roadways, tend to suffer some of the worst air quality in Las Vegas.

Is Las Vegas doomed to poor air quality?

According to the latest report from the American Lung Association, ozone levels are getting worse. Las Vegas is now ranked as the 9^th most ozone-polluted city in the US, up from 13^ththe previous year. They also stated that it was the 25^th dirtiest state when considering Particulate Matter or PM2.5 pollution.

In retaliation, Clark Country said that it had been greatly affected by the raging wildfires in California and they were a considerable source of air pollution. A spokesperson went on to say that with the exception of the wildfires in 2017 and 2018, the levels of ozone have actually been on the decline for the past several years. Ozone is a gas that exists naturally in the atmosphere but can build up at ground-level during the day because of high temperatures, chemical vapours and vehicle emissions. It is produced at an increased rate during the summer months when the climate is hotter and sunnier.

How does the poor air quality in Las Vegas affect the health of its residents?

People’s health risk from air pollution varies widely depending on age, where they live, their underlying health, and other factors. The concentrations of the pollutants and length of time subject to exposure also can change the outcome.

Populations most at risk of health problems related to air pollution:

• People with pre-existing lung diseases, such as asthma, chronic bronchitis, emphysema, and chronic obstructive pulmonary disease
• Infants and young children under the age of 14 years as their organs are not yet fully developed.
• People who work or exercise outdoors
• Adults over 65
• People with a cardiovascular disease
• People who lack access to health care
• People who smoke or are exposed to second-hand smoke
• People working in occupations where there is high exposure to contaminated air
• People who spend a lot of time near busy roadways.

Studies have shown that people who live, work, or attend school near major roadways have an increased incidence and severity of health problems, including asthma, cardiovascular disease, low birth weight, premature babies, reduced lung function and impaired lung development in children, and premature mortality.

Areas within 1,000 to 1,600 feet from highways and other major roads are most impacted by traffic-related pollution. An estimated 30 to 45 per cent of people in large North American cities live within such areas.

Does Las Vegas have an air pollution problem?

In recent years, Las Vegas air quality has averaged a “good” US AQI rating, indicating that residents generally breathe air that poses little to no risk to health. Despite optimistic annual averages, daily fluctuations are a cause for concern. In 2019, Las Vegas failed to meet federal attainment levels for daily ozone and PM2.5 levels, meaning that the number of unhealthy days for each pollutant was in excess of 3.2 days. From 2016 to 2018, there was a weighted average of 30.2 days of unhealthy ozone, and 4.3 days of unhealthy PM2.5.1 As a result of this “severe nonattainment”, Las Vegas was rated an “F” for both daily PM2.5 and ozone levels.

Clark County, of which Las Vegas is the county seat, has never met attainment levels for ozone.1 2014 to 2016 was the closest the city ever got when ozone levels were more than 6 times the federal allowance. Out of 229 metropolitan areas included in the American Lung Association’s State of the Air report, the Las Vegas-Henderson area ranked 9 for worst ozone pollution nationally. Las Vegas’s unhealthy ozone pollution affects everyone. The most common health effects of breathing high levels of ozone include chest pain, coughing, airway inflammation, and difficulty breathing.

Sensitive groups, including children, the elderly, and those with heart or lung disease tend to be disproportionately hurt by nonattainment levels. Clark County has 1,292,764 residents classified as sensitive to air pollution, out of a total population of 2,231,647 residents – more residents are labelled sensitive in Clark than not sensitive. These individuals are more likely to experience severe adverse health effects and hospitalisations from heightened ozone levels.

Has the COVID-19 pandemic affected the air quality in Las Vegas?

Air quality has surely improved due to there being less traffic on the roads. All non-essential businesses were closed in Clark County because of the pandemic.

This resulted in a 33 per cent decrease in the amount of particulate matter (PM2.5) and nitrogen dioxide (NO₂). The Regional Transport Commission of Southern Nevada also reported a decline in traffic using two of the busiest interstate highways. Interstate 15 was reported to have 73 per cent fewer vehicles using it than before the restrictions came into force.

Based on information from the previous five years, it can be seen that PM2.5, nitrogen dioxide and ozone levels were all lower because of the new restrictions. Overall, the quality of air has been improving over the past decade but it is too much to hope that these new lower levels will continue after the restrictions are lifted.

+ Article Resources
[1] Environmental Protection Agency (EPA). (2020). 2015 Revision to 2008 ozone National Ambient Air Quality Standards (NAAQS) related documents.
[2] Lochhead C. (2020, June 22). Nevada adopting stricter car pollution standards.
[3] Census. (2000). Population change and distribution.
[4] World Climate. (2020). Average Weather Data for Las Vegas, Nevada.