China’s fight against Air pollution could be hampered by increased levels of ozone in the lower atmosphere.

The bad news is, ozone levels in the lower atmosphere are rising. In 2013, China released a 5-year National action plan for improving air quality, with specific focus on regions such as Beijing, Yangtze River Delta (around Shanghai) and Pearl River Delta (around Guangzhou). China seems to be on track towards achieving this goal, as reports released in the first half of 2015 showed a 15% decrease in PM2.5 compared to the same period last year.

This trend has continued into Q3 2015 where air quality data released by China’s Ministry of environmental protection shows an overall improvement in PM2.5 levels by 18.5%, across 74 cities as compared to the 3rd quarter of last year.

But this is the good news. The bad news is, ozone levels in the lower atmosphere are rising. In the first half of 2015, ozone levels reached 145µg/m3 (micrograms/ cubic meter), which is a 4.3% increase from the previous year. Ozone is not visible, meaning the clearance of smog does not imply it’s time to ditch your pollution mask. What’s more, on those clear days, ozone levels could be even higher, as the formation of ozone requires sunlight.

We all thought ozone was a good thing...

Very little is known about ozone at ground level. Ozone is safe in the higher levels of the atmosphere, where it protects the earth against UV rays.

However, when it gets to ground level, it pollutes the air and even has adverse effects on health. Ground-level ozone is formed when light from the sun reacts with pollutants such as Nitrogen oxides, carbons and other pollutants.

There’s higher concentration of ground ozone in heavily populated areas and areas with more vehicles, as such areas tend to have more pm2.5 and other polluting gases in the air. When ozone mixes with these pollutants the result is heavy smog.

Different studies on the effects of ozone show that short term exposure to ozone will cause respiratory problems, burning sensation in the eyes, coughing headaches increased sensitivity to allergens, among other symptoms. In the long term, exposure to ozone pollution will cause lung disease, higher incidences of asthma and higher mortality. The effects of ozone (O3) may also be enhanced by particulate matter. These effects can be felt even in remote areas as though ozone pollution happens in areas with industries, air pollutants can be carried there by wind.

The fight still continues

This fresh focus on ozone pollution has definitely meant the need to shift gears in the fight against pollution in China. According to He Kebin, head of School of Environment at Tsinghua University, higher ozone levels on the ground will mean more measures are required to tackle the pollution problem in china.

This news emphasizes the need for using masks that are capable of filtering small particles of pollutants. At a size of 2.00 µg/m3, ozone is even smaller than PM2.5 and is thus more difficult to filter using normal masks.

As well, though the news on annual and quarterly PM2.5 is good, the levels are still quite high especially when taken on a daily basis. For instance, Shenyang, which is in the Northeastern part of China, recorded PM2.5 levels of 1400 µg /m3 in the first weekend of November 2015, which led to heavy smog. This is 140 times higher than WHO’s daily recommended levels of 10 µg/m3. At this level, even low risk individuals would be affected unless they are wearing a pollution mask that can filter PM2.5 and other polluting gases.

Lastly, protect yourself while indoors as indoor ozone contributes to at least 25 and 60% of your daily ozone intake.