For a while there, ionic air purifiers took the world of air purification by storm. People were drawn in by their quiet operation, the fact that they don’t use or require filters, and for their energy efficiency. It seemed as if HEPA air purifiers had some legitimate competition for the very first time. It didn’t take long, though, for news about the problems with ionic air purifiers to spread. The biggest concern that haunts the supposed benefits of these machines is their close association with ozone. Indeed, ionic air purifiers produce ozone as a byproduct – and ozone is a proven lung irritant that flies in the face of improving indoor air quality.

The Problem with Ozone

To understand the growing concern that many people have about ionic air purifiers, it is necessary to get a handle on why ozone is so problematic. Most of us are familiar with ozone due to the ozone layer, the much talked about protective bubble that envelops the Earth’s atmosphere. Nearly everybody knows about the ever increasing concerns about ozone layer depletion and what it means for the health and safety of people around the world. In that regard, ozone is a very important and necessary molecule in the Earth’s stratosphere; it’s when ozone gets into the air we breathe that it creates trouble.

The Environmental Protection Agency (EPA) has issued warnings regarding the dangers of ozone exposure. Basically, breathing in ozone can cause a laundry list of health problems. Chief among these health problems are coughing, shortness of breath, chest pain and an irritated throat. Breathing in ozone on a regular basis can exacerbate or worsen existing respiratory conditions including asthma and allergies. Without a doubt, all of us are better off avoiding ozone at all costs – yet an air purifier that is designed to clean the air we breathe produces it as a byproduct.

Pyramid of effects caused by ozone

The relationship between the severity of the effect and the proportion of the population experiencing the effect can be presented as a pyramid. Many individuals experience the least serious, most common effects shown at the bottom of the pyramid. Fewer individuals experience the more severe effects such as hospitalization or death. (EPA)

Effects of ozone on lung function

These photos show a healthy lung airway (left) and an inflamed lung airway (right). (EPA)

Ozone Pollution and Your Patients' Health - https://www.epa.gov/ozone-pollution-and-your-patients-health/end-ozone-pollution-and-your-patients-health-training

How Ionic Air Purifiers Work

Ionic air purifiers work in a completely different way than HEPA air purifiers. They release a continuous flow of negatively charged ions into the air. Those ions connect with airborne particulates, making them negatively charged as well. Over time, all of those negatively charged particles group together, become heavy, and fall to the ground or onto nearby surfaces. They are removed from the air, but not removed from the room. Instead, they create a film of sorts on things around a room and can even be stirred back up into the air.

Ozone and Ionic Air Purifiers: A Troubling Connection

As beneficial as ionic air purifiers may sound, they come with one very negative side effect: ozone production. In order to produce the negatively charged ions that they do, these machines must emit ozone as a byproduct. Considering that the American Lung Association (ALA) has issued stern warnings about exposure to ozone in the past, it stands to reason that using an ionic air purifier just doesn’t make any sense. Why introduce such an irritant into the air in your home if you can help it?

AB 2276 Air Cleaner Ozone Regulation - https://ww3.arb.ca.gov/research/indoor/aircleaners/comments/ala.pdf

The UC Irvine Study

During their study, researchers at University of California at Irvine tested many different types of air purifiers under controlled conditions. The areas in which these purifiers were placed included bedrooms, bathrooms, offices and even cars. At each location, the purifier was turned on and the levels of ozone in the area were tracked using special devices. In many cases, the levels of ozone that were ultimately produced were far higher than those necessary to issue a public health alert – and were kept bottled up in the home, meaning that they did not dissipate quickly or easily.

In the worst cases, the ozone level reached an astonishing 350 parts per billion; this is an amount that is more than ample to trigger a Stage Two smog alert if discovered outdoors. To put that into perspective, the last time a Stage Two smog alert was issued in the state of California was 1988. It is an extraordinarily high level, and is considered quite dangerous and deleterious to the health of people exposed to it. Considering that an air purifier can produce similar results inside a home is truly worrisome.

Hazardous Ozone-Generating "Air Purifiers"

Not all air-cleaning devices are appropriate for home use — some can be harmful to human health. The ARB recommends that ozone generators, air cleaners that intentionally produce ozone, not be used in the home. Ozone is a gas that can cause health problems, including respiratory tract irritation and breathing difficulty (Ozone and Health). In the US, some manufacturers have submitted test results and obtained ARB certification of their air cleaning devices as required under our regulation. The list of California air cleaners certified are based on their electrical safety and their low ozone emissions.

UCI Study: Ionic Air Purifiers May Exacerbate Health Problems

Researchers at the University of California, Irvine, have determined that in poorly-ventilated rooms, air purifiers that produce even a few milligrams of ozone per hour may exacerbate health problems. The Mayo Clinic has also found that ozone can make asthma and other respiratory problems worse and recommends against ozone generators and ionizing air purifiers that produce the molecules. Instead, people should use HEPA air purifiers, which do not emit ozone.

What is Ozone?

The Environmental Protection Agency differentiates between good ozone and bad ozone. Good ozone is found in the upper atmosphere, the ozone layer, which protects the Earth from the sun’s harmful radiation. Bad ozone is found close to the Earth’s surface. This low level ozone is regarded by the EPA and the World Health Organization as an environmental pollutant.

The ozone molecule contains three oxygen atoms. Two of them form the familiar oxygen molecule. The third atom may detach and react with other molecules in the environment. As noted by the Mayo Clinic, inhaling even small amounts of ozone can be irritating to one’s lungs. Ozone can cause coughing or shortness of breath, can irritate one’s throat, and can increase the risk of respiratory infection.

What Produces Ozone?

Ozone may be emitted as a byproduct of an air purifier’s operation. Ionic air purifiers are the most common culprit. Ionic air purifiers charge airborne particles, attracting them to metal electrodes. In the process, they emit ozone as a byproduct. Though it varies by purifier, some ionizers may produce a few milligrams every hour. The study found that this ozone accumulates indoors, leading to higher concentrations than is considered safe. HEPA air purifiers, however, do not emit ozone.

Study Findings

The UCI study, published in the Journal of the Air & Waste Management Association, found that in rooms with poor ventilation, an air purifier that emits even a tiny amount of ozone per hour can lead to levels that exceed public safety guidelines. Significantly, it also demonstrated that ozone emitted from air purifiers adds to the ozone already present, resulting in a cumulatively higher ozone level. This means that people using some ionic air purifiers to reduce allergens and other pollutants may actually be causing themselves more harm. To come to this conclusion, the researchers tested several kinds of indoor air purifiers at 40% or 50% relative humidity, cataloguing their levels of ozone production. They tested the purifiers in various indoor environments, including bedrooms, bathrooms, offices, and cars. They placed the air purifier in a room, turned it on, and recorded the increasing ozone concentration until it leveled off. In many cases, the indoor level significantly exceeded outdoor safety guidelines. Some even reached a level that would have triggered a Stage 2 smog alert if detected outside. The largest increases in ozone concentration occurred in small, poorly-ventilated rooms, especially those with glossy ceramic tiles and other materials that react slowly with ozone.

Other Research

In a 2009 study published in the New England Journal of Medicine, “Long-Term Ozone Exposure and Mortality,” researchers found that people who live in cities with high concentrations of ozone have a 30% greater annual risk of dying from respiratory illness. The study was especially notable because it looked at the long-term health impact of ozone concentrations, cataloguing deaths from 1977 through 2000. It’s the first study to quantify the deleterious health effects of ozone exposure. It’s clear that people should try to reduce their exposure to ozone, so they need to choose an air purifier accordingly.

Traffic-Related Air Pollution, Particulate Matter, and Autism

Exposure to traffic-related air pollution, nitrogen dioxide, PM2.5, and PM10 during pregnancy and during the first year of life was associated with autism. Further epidemiological and toxicological examinations of likely biological pathways will help determine whether these associations are causal. Volk, H.E., Lurmann, F; Penfold, B; Hertz-Picciotto, Irva; McConnell,Rob, (2013) JAMA Psychiatry. 2013;70(1):71-77. Published online November 26, 2012. doi:10.1001/jamapsychiatry.2013.266

IARC: Outdoor air pollution a leading environmental cause of cancer deaths

Lyon/Geneva, 17 October 2013 – The specialized cancer agency of the World Health Organization, the International Agency for Research on Cancer (IARC), announced today that it has classified outdoor air pollution as carcinogenic to humans (Group 1). After thoroughly reviewing the latest available scientific literature, the world’s leading experts convened by the IARC Monographs Programme concluded that there is sufficient evidence that exposure to outdoor air pollution causes lung cancer (Group 1). They also noted a positive association with an increased risk of bladder cancer. Particulate matter, a major component of outdoor air pollution, was evaluated separately and was also classified as carcinogenic to humans (Group 1). The IARC evaluation showed an increasing risk of lung cancer with increasing levels of exposure to particulate matter and air pollution. Although the composition of air pollution and levels of exposure can vary dramatically between locations, the conclusions of the Working Group apply to all regions of the world.

Air Pollution and Cancer IARC Scientific Publication No. 161 - http://publications.iarc.fr/Book-And-Report-Series/Iarc-Scientific-Publications/Air-Pollution-And-Cancer-2013