Air pollution: Coming to terms with what’s acceptable, what isn’t

It is safe to say there will never be such thing as zero polluted air. Even Mother Nature adds her own share: Think dust storms, volcanic eruptions and lightning strikes.

With this knowledge, what amount of pollution in the air, then, is acceptable?

To try to provide an answer, that would seem to be contingent on who, first, is looking at the situation and, second, what process is or what processes are employed to determine what that answer is.

First and foremost though it is important to keep in mind there are many different types of air pollution.

So, the question becomes what air pollutant type to focus on.

The more common ones seem to be ozone, fine particulate matter, oxides of nitrogen, nitrogen dioxide, sulfur dioxide, hydrocarbons and volatile organic compounds and, one could add to that list, carbon (including black and brown), carbon monoxide and methane. There is certainly no shortage of pollutant emissions to choose from. The two main ones appear to be fine particulate matter and ozone.

Next we want to look at what the pollutant-in-question’s effect is on public health. How unhealthy is it to human life when inhaled – and at what concentration over what period of time? What level or amount in the air is considered safe? What strategy requires being put into action or, stated differently, what action plan will be the most effective in the shortest amount of time – to get the pollutant in question under control? In reference to this, this means meeting an established, agreed-upon health standard or threshold. Things of this nature. So, you can see there are numerous factors to consider.

Now let’s look at those standards. In the United States, the two pollutants of most concern are particulate matter 2.5 micrometers in size (or PM 2.5) and ozone. Ozone, incidentally, is a key building block of smog. The standards are 35 micrograms per cubic meter of air (the 24-hour national health standard) and 12 micrograms per cubic meter of air (the annual national health standard) for PM 2.5 and for ozone, meanwhile, the 8-hour national health standard is 70 parts per billion parts of air. It should be noted that different health standards for different air pollutants have been established at different times.

Take ozone, for example. Prior to Oct. 1, 2015 the National Ambient Air Quality Standard or NAAQS was 75 parts per billion (ppb), and before that it was an even higher – or less stringent depending on how you want to look at it – 84 ppb. The 84 ppb standard was in effect prior to 2008, the year the 75 ppb standard went into effect.

As it can be seen, the standards change. Some will argue that the 70-ppb standard isn’t even stringent enough, this based on health studies done to determine what is the acceptable limit. They believe the standard should be set at a maximum 60 ppb. Ozone can trigger asthma attacks, can lead to chronic obstructive pulmonary disease (COPD), can cause coughing, wheezing and heart issues like ischaemic heart disease, and can contribute to cancer and even death. Which is why ozone is no doubt considered one of the worst of the air-pollutant emissions around – period.

Turning now to fine particulate matter air pollution (the specks and aerosols themselves up to 30 times smaller than the width of a human hair) is invisible to the eye. It’s no less damaging to human health than ozone and probably, if not likely, even more so because of its ability to lodge deep in the lung, enter the bloodstream and be transported to various organs in the body as well as to the brain. PM 2.5 has been found to affect cognitive ability, even.

According to at least one study, estimates are that outdoor PM 2.5 is responsible for contributing to the deaths of over four million people globally in 2018.

“Researchers estimated that exposure to particulate matter from fossil fuel emissions accounted for 18 percent of total global deaths in 2018 – a little less than 1 out of 5,” wrote Leah Burrows in “Deaths from fossil fuel emissions higher than previously thought,” a Feb. 9, 2021 Harvard John A. Paulson School of Engineering and Applied Sciences press release, and added, “The study greatly increases estimates of the numbers killed by air pollution. The most recent Global Burden of Disease Study, the largest and most comprehensive study on the causes of global mortality, put the total number of global deaths from all outdoor airborne particulate matter – including dust and smoke from wildfires and agricultural burns – at 4.2 million.”

Some believe that due to PM 2.5’s ability to penetrate lung tissue and cause organ and brain damage, and for these reasons, there can be no level or amount in the air that is deemed safe. Which, to them, means that regardless of threshold, this pollutant when suspended in the air is simply unsafe.

All things considered, maybe the better question to ask would be is not so much what limit or standard or threshold is acceptable and what is not, but something more along the lines of what are we willing to or what can we live with?

When these answers for all the air-pollutant emissions in question are definitively determined, then we’ll know. Hopefully, we’ll have these answers soon!

Oh, and one last – and important – observation: Being that that acceptable air pollution limit has yet to be found, this could help explain why it is that those tasked with reaching universal agreement on how best to tackle global warming and climate change challenges has been so difficult. Just saying.


In an earlier version of this post, the passage “for 18 percent” was inadvertently omitted from the “Researchers estimated that exposure to particulate matter from fossil fuel emissions accounted for 18 percent of total global deaths in 2018 – a little less than 1 out of 5,” quote above, the original source of that statement being the Feb. 9, 2021 Harvard John A. Paulson School of Engineering and Applied Sciences press release, “Deaths from fossil fuel emissions higher than previously thought.” All wording is now correct.

– Alan Kandel

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This post was last updated on Oct. 14, 2022 at 1:40 p.m. Pacific Daylight Time.

The material in this press release comes from the originating research organization. Content may be edited for style and length. Want more? Sign up for our daily email.