CSE Press Release World Environment Day special

June 03, 2017


On the eve of the World Environment Day, CSE warns no one is safe from deadly ozone pollution

Increased heat wave and rising summer temperatures, inevitable with climate change, is worsening this trend

  • This is bad news for those suffering from asthma and respiratory problems. It is dangerous if ozone increases even for a short duration

  • Rising NOx levels and volatile gases in the air, primarily from vehicles and industry, form the recipe for ozone when exposed to intense sunlight and high temperature

  • What is needed -- fast-track time-bound implementation of pollution source-wise comprehensive action plan to reduce the cocktail of gases from vehicles and industry that form ozone in the air

New Delhi, June 3, 2017: Delhi has witnessed significant ozone build-up this summer, adding to the public health risk -- shows a latest analysis done by Centre for Science and Environment (CSE). Building up to the World Environment Day, CSE has analysed the real-time air quality data available from the key monitoring locations of Delhi Pollution Control Committee for the summer months of 2016 and 2017 (see CSE’s ozone factsheet at http://www.cseindia.org/userfiles/Ozone-factsheet-29.5.2017.pdf).

This shows ozone pollution in the city is worsening progressively with the onset of summer. With high pollution levels and growing heat stress due to climate change, the ozone level is frequently exceeding the standards and rising to poor and very poor levels – as classified by the National Air Quality Index (NAQI).

Additional analysis also shows heat waves and sunshine have increased the frequency of days with unhealthy levels of ozone. This has become worse this summer. Ground-level ozone is not directly emitted by any source. This is formed when oxides of nitrogen (NOX) and a range of volatile gases, primarily from vehicles and other sources, are exposed to each other in sunlight.

Warm and stagnant air increases the formation of ozone. Ozone is extremely hazardous for human health. All neighbourhoods in Delhi – rich and poor – are at risk.

According to Anumita Roychowdhury, executive director, research and advocacy and head of CSE’s air pollution programme: “Delhi and the National Capital Region (NCR) are in the grip of multi-pollutant crisis. Even before the health risk from particulate matter could be addressed, deadly ozone has raised its ugly head in Delhi and NCR. Without a time-bound implementation strategy and preventive action, this can deepen into serious public health crisis. This will spare neither the rich nor the poor.”

W*hat has CSE found?

CSE has analysed ozone data from February to May to understand the ozone build-up during summer. It has considered ozone data from the automatic monitoring stations of the Delhi Pollution Control Committee. Continuous data is available from R K Puram, Punjabi Bagh and AnandVihar from February to May, 2017. Data from other stations is sporadic. The ozone data have also been compared for the months of April and May of 2016 and 2017. Limited data is available from the NCR. This has pointed towards worrying trends in the city. 

Ozone spikes as summer progresses: As summer progressed from February to May this year, the ozone built up rapidly and the number of days exceeding the ozone standard increased. The share of days violating the 8-hour CPCB standard of 100 microgramme per cubic metre in February was 12 per cent – this increased to 19 per cent in March, 52 per cent in April and finally a whopping 77 per cent in May

While ozone levels have increased steadily with the onset of summer, it doubled up very quickly in most locations as soon as the heat wave hit Delhi in May. On several occasions and several locations, very high peak levels – 3times the standards -- have been noted. This is of serious concern as even short duration exposure to high ozone levels can cause great harm. This is one of the reasons why ozone standards are set for eight-hour average as well as one-hour average.

Days violating the ozone standard are higher this year: The number of days in April and May, 2017 violating the eight-hour standard is higher this year compared to the previous year. In 2017 summer, as much as 64 per cent of days during April and May violated the standard as opposed to 50 per cent of days during April and May in 2016. The problem is growing steadily. 

More days in ‘very poor’ category this year: Not only have the total numbers of days that have violated the standards increased this year, the severity of the problem has also grown. This summer (April-May), 8 per cent of days are in ‘very poor’ category – which is up to 7.5 times the standards, as opposed to 4 per cent during the same months in 2016. However, the summer of 2016 had higher number of days in the ‘poor’ category.

Heat wave, high solar radiation with increased ambient temperature during summer making the problem worse: CSE has analysed the relationship between ozone build-up on one hand and increased solar radiation and rising ambient temperature on the other. Due to higher temperature and solar radiation, ozone concentration has also increased. For example, in April 2017, as the temperature increased from 27°C on April 9 to 32°C on April 14, the daytime ozone levels increased by 134 per cent or 2.34 times -- rising from 90 to 211 microgramme per cubic metre. A similar trend is observed in May. When temperature rose from 32°C on May 3 to 36°C on May 8, the daytime ozone concentration increased by 130 per cent or 2.3 times, spiking from 100 to 230 microgramme per cubic metre. This is ominous. With climate change and higher frequency of extreme weather events, such trends will put citizens at serious public health risk. 

Residential neighbourhoods where people live are more vulnerable: Micro-mapping of ozone levels across the city shows high vulnerability of residential areas. Residential **areas of RK Puram and Punjabi Bagh have high ozone concentrations – much higher than the commercial and transport hub of AnandVihar. This is a very serious health concern.

RK Puram experienced one of the highest concentrations of ozone -- 337 microgramme per cubic metre -- which is more than three times the eight –hour standard. As much as 82 per cent of days in April and 100 per cent or all days in May have violated the safe standard. 

Punjabi Bagh has experienced the highest eight-hour average concentration of ozone, at 416 microgramme per cubic metre -- more than four times the safe standard. As much as 78 per cent of days in April were violated. The data for May for this location was not available on the CPCB website.  

In Anand Vihar, a commercial and a transport hub, the levels have gone up to twice the standard. About 17 per cent of days exceeded the safe standard in April followed by 68 per cent in May.

Ozone is becoming an NCR-wide problem: Ozone monitoring is very limited nation-wide. Not all cities monitor ozone. Data available for NCR shows that while 67 per cent of days in Delhi during April and May of 2017 have violated the standards, 23 per cent of days in Gurugram, 62 per cent in Ghaziabad, and 35 per cent in Faridabad have also violated it. This is becoming a regional problem and demands regional action. 

Why should we worry about ozone?

Early deaths due to ozone pollution are the highest in India: The new burden of disease study from Health Effect Institute has shown that early deaths due to ozone have jumped by 148 per cent in India. Ozone aggravates respiratory problems, especially chronic obstructive pulmonary disease (COPD). The HEI scientists used the chemical transport model for estimating the ozone, but the evidence of increasing ozone levels in India, especially in north India, is seen from the available measurements. 

According to scientists, formation of ozone is expected to be higher in countries in tropics and sub-tropics and near the equator. To some extent, rising temperature is also aggravating this trend. India will be well advised to take early and stringent steps to control ozone precursors which are very difficult to control. This means stringent control of gaseous emissions from combustion sources including vehicles. Ozone precursors like nitrogen oxides, carbon monoxides and volatile organic compounds also have serious local public health impacts.

Ozone is an extremely harmful gas, just a few hours of exposure to it can trigger serious health problems. It is particularly harmful for outdoor activities. It can have immediate health impact especially among those who are already suffering from respiratory and asthmatic problems even for short duration exposure. Ozone worsens symptoms of asthma, leads to lung function impairment and damages lung tissues. Chest pain, coughing, nausea, headaches and chest congestion are common symptoms. It can even worsen heart disease, bronchitis and emphysema. It increases emergency hospital visits and admissions related to respiratory diseases. 

A study by the University of Southern California and reported in Lancet, has found that in high-ozone areas the relative risk of developing asthma in children playing three or more sports was more compared to children playing no sports. Outdoor heavy exercise is not recommended -- with every breath, athletes particularly take in 10 to 20 times more air, and thus pollutants, as sedentary people.

Scientists inform that ozone is a powerful oxidiser, which means it can damage cells in a process akin to rusting. Children and the elderly are at special risk. There is a strong association between ozone and daily premature death counts. Those with pre-existing diseases and lung diseases are at serious risk. Growing concentrations of nitrogen oxide and volatile organic compounds from combustion sources, especially from the explosive increase in diesel vehicles is adding to the deadly recipe of ozone in hot and extreme climate. Also, ozone that gets created in the polluted environs of the city can also drift depending on the wind direction towards cleaner environs in rural periphery and begins to accumulate as it has less chances of reacting with other pollutants in cleaner environment. Hence it builds up fast at the outskirts. It is known to damage crops.

What do other governments do?

Ozone is included in the daily smog and health alert programmes in countries such as Mexico, the US, China among others. In Mexico City, the elderly, children and those suffering from respiratory and cardiac problems are advised to stay indoors when levels of ozone go up. The US-based National Research Council, part of the National Academies of Science, has recommended that local health authorities should keep the harmful effects of ozone in mind when advising people on polluted days. The US has therefore tightened the ozone standards. 

Need urgent action

Delhi and NCR needs much high degree of health protection for all and especially the high risk groups including the elderly, children, outdoor workers and people with asthma and lung disease. Cost of inaction can be very high. Governments must have its implementation strategy for priority measures in place before the next winter: 

  • Finalise and implement pollution source-wise comprehensive action plan directed by the Supreme Court in Delhi and NCR. . This should include targeted reduction of gaseous emissions from vehicles, industry and power plants. Need stringent measures to reduce nitrogen oxide and a range of volatile hydrocarbons.

  • Ensure timey implementation of BS VI emissions standards and control dieselization of vehicles segment to control NOx emissions.

  • Need time bound implementation to scale up public transport, walking and cycling to reduce vehicles usage and numbers.

  • Issue health alert on bad ozone days and link to graded response action plan.