Clear The Air News Blog Rotating Header Image

Nitrogen Oxide

Hong Kong can create its own smog, researchers say

Scientists from Hong Kong and Macau found one day in which pollutants were formed when dirty air was not blowing from the north

Smoggy days are often blamed on regional pollution and weather, but at least one recent scientific study has shown that the city can, under the right conditions, “form its own smog”.

The study by Hong Kong and Macau air scientists argued that a rapid build-up of particulate matter in the air – a key component of smog – was possible even in the absence of northerly winds that can transport pollutants from afar.

The evidence boiled down to at least one particular sunny September day in Hong Kong in which a “land-sea breeze” pattern formed along with weak winds far below average speeds.

The scientists observed a rapid rise of photochemical activity during mid-afternoon, in which ozone and nitrogen dioxide skyrocketed along with increasing sunshine.

“It is clear that there was a rapid increase in particulate matter (PM) concentration on this day when we were not really affected by external meteorological conditions. It’s not easy to argue in this case that winds were blowing PM to Hong Kong from the region ,” said co-author Professor Chan Chak-keung, dean of City University’s school of energy and environment.

The culprits, he said, were most likely local sources such as vehicles or industrial emissions, which contain nitrogen oxides and volatile organic compounds. The latter pollutant is also found in products such as organic solvents, paints and printer inks.

Chan’s team investigated “episodes” – days with high PM concentrations – in one-month periods in each of the four seasons from 2011 to 2012 at the University of Science and Technology’s air quality research supersite.

Other episodes across the seasons were also observed with high local photochemical activity, but those days also came under the influence of transported air from the north, making it less clear what was actually local or regional.

The paper was published in scientific journal Atmospheric Chemistry and Physics in November.

“Of course, regional sources play a role but [this research] shows that under the right conditions, PM can build up and Hong Kong can form its own photochemical smog.”

Photochemical smog is created when nitrogen oxides react with volatile organic compounds in the air under sunlight. It leads to the formation of ozone. This hazardous pollutant facilitates the formation of the tiny particles, small enough to be inhaled deep into the lungs and even into the bloodstream.

The particulate matter in the air lowers visibility, turning the sky smoggy and gives it a lurid orange tint at dusk.

The Environmental Protection Department usually points to meteorological influences such as northeast monsoons when the air quality health index hits “very high” health risk levels.

During a bout of high pollution last Thursday, it said: “Hong Kong is being affected by an airstream with higher background pollutant concentrations. The light wind hinders effective dispersion of air pollutants.”

It added that the formation of ozone and fine particulates during the daytime resulted in high pollution in the region.

Chan said most smoggy days were doubtless a result of regional factors or pollution. But he said the study’s findings warranted more research on how PM was formed and pinpointing its sources.

Source URL:

How scientists cracked the puzzle of Beijing’s wintertime smog

Sulphate levels in Chinese capital’s air similar to those produced by volcanic eruptions

Levels of a pollutant linked to diarrhoea and global cooling in Beijing’s notorious smog can approach those produced by volcanic eruptions, according to a newly published international study.

Researchers from Germany, the United States and China recorded extremely high concentrations of sulphate on the Tsinghua University campus in January 2013 during a joint study of air pollution in the Chinese capital.

Sulphate is a salt of sulphuric acid that, in nature, is usually formed in the atmosphere after a volcanic eruption.

The sulphate concentration on the roof of one Tsinghua building hit 300 micrograms per cubic metre of air, comparable to the fallout from the eruption of the Eyjafjallajokull volcano in Iceland in 2010, which produced an average, near-surface concentration of 400 micrograms over Scandinavia.

That might explain why some people experience diarrhoea, a typical effect of sulphate poisoning, on smoggy days, alongside other symptoms linked to air pollution.

But the high levels of sulphate in the smog that plagues Beijing each winter puzzled the researchers.

In nature, sulphate is formed when massive amounts of sulphur are thrust high into the atmosphere by a volcanic eruption and transformed by sunlight in a process known as photochemistry.

“No theory could explain why it happened during a cold, dim winter in Beijing with little photochemistry going on,” said Dr Su Hang, a researcher at the Max Planck Institute for Chemistry in Mainz, Germany, and one of the scientists involved in the study.

In a paper published in the journal Sciences Advances on Wednesday, Su and his colleagues pinpointed a culprit: nitrogen oxides – a family of pollutants mainly created by industrial and vehicular emissions.

Nitrogen oxides, including nitric oxide and nitrogen dioxide, could bind with water vapour and create many floating liquid droplets that would not freeze in sub-zero temperatures. The airborne droplets then served as a chemical reactor, absorbing sulphur dioxide from the atmosphere and turning it into sulphate. The more sulphate produced, the bigger the droplet and the faster the chemical reaction.

“It was like a chain reaction,” Su said. “Once started, it would not stop.”

That made the smog in Beijing different from the photochemical smog, driven by sunlight, that troubled Los Angeles in the 1970s.

The researchers said the amount of man-made air pollutants in China’s lower atmosphere had reached a level unprecedented in human history and that was triggering chemical reactions previously thought impossible.

In Beijing, Su said, smog could develop rapidly at night, and residents sometimes woke up to find the air outside “as thick as soup”.

Sulphate is also believed to play an important role in planet cooling, with scientists linking the massive spread of sulphate in the atmosphere after volcanic eruptions to numerous episodes of global cooling throughout history due to the chemical’s ability to reflect sunlight back into outer space almost as effectively as a mirror.

Whether the smog in China could help slow global warming required further investigation, the researchers said.

The researchers urged the authorities to treat nitrogen oxides as a major enemy in the battle against smog – with a focus on cutting industrial and vehicular emissions – because the chemistry at work in haze not only produced sulphate but also lots of nitrate, which could cause oxygen levels in the blood to drop, causing dizziness, headaches or even death.

“Reducing the nitrogen oxides can shoot several birds with one stone,” Su said.

Source URL:

New watered-down EU air pollution targets

Compared to the Commission’s proposal, the relaxed targets finally agreed by member states and parliament will result in thousands of additional cases of premature death.

On 30 June, the last day of the Dutch EU Presidency, the Council and the European Parliament reached a provisional agreement on a new National Emission Ceilings (NEC) directive.

The new directive establishes national limits for the emissions of five pollutants: sulphur dioxide, nitrogen oxides, non-methane volatile organic compounds (NMVOC), ammonia and fine particulate matter (PM2.5). The limits are set as binding National Emission Reduction Commitments (NERC), expressed as percentage reductions from the base year 2005.

The NERCs for 2020 to 2029 are identical to those to which the member states are already committed in the revised Gothenburg protocol under the Convention on Long-Range Transboundary Air Pollution. Since these limits in many cases allow emissions that are even higher that what is expected to result from countries implementing already adopted legislation, they have widely been criticised for their weakness.

More importantly, new stricter NERCs from 2030 have now been agreed. These are set to reduce the health impacts of air pollution by 49.6 per cent in 2030, compared to 2005. While the Commission and the Parliament aimed for an ambition level that would result in a 52 per cent reduction in premature deaths from air pollution, the Council (i.e. the member states) argued for a significantly less ambitious target of 48 per cent. The compromise now agreed has been estimated to result in some 10,000 additional annual premature deaths in 2030, on top of more than a quarter of a million annual premature deaths that are expected to remain if the Commission’s proposal was to be implemented.

Looking at the specific NERCs for each member state, and comparing these with the Commission’s proposal, it was agreed to lower 79 of the 140 targets for 2030, while agreeing to keep 40 at the level proposed by the Commission, and setting more ambitious targets in just 21 cases (see Table).

At the bottom of the league among member states we find Bulgaria, Greece and Romania, who have all chosen to weaken their NERCs for all five pollutants, while Austria, Denmark, Italy, Poland and the UK lowered targets for four of the pollutants.

In contrast, Finland accepted all its targets, closely followed by Belgium, France and Sweden, which stick to four out of the five targets. As icing on the cake, Finland has opted for a tougher target for ammonia, and Sweden has opted for tougher targets for both sulphur dioxide and PM2.5.

For the EU as a whole, ammonia and NMVOC are the pollutants for which the ambition level has been downgraded the most, by six percentage points. This outcome for ammonia is particularly remarkable as the emission cuts achieved so far for this pollutant have been very modest compared to those for the other pollutants, especially considering that the proposed reduction target for 2030 was much less ambitious than for the other pollutants.

Member states managed to remove the ozone precursor methane completely from the directive, despite objections from the Parliament and the Commission. Here, the industrial farming lobby was instrumental in pushing through both the drastically lowered ambition for ammonia and the removal of methane.

Moreover, member states succeeded in introducing a variety of additional flexibilities in order to make it easier for them to comply. While the Commission had already included three flexibilities in its proposal, five more have now been added to the final text. Environmental organisations have strongly criticised these flexibilities, claiming that they will result in higher emissions; delayed reductions; more avoidable deaths and environmental damage; more unnecessary administration; and an unenforceable directive.

Because of the lax 2020 targets, and to better ensure that countries really are on track to meet their 2030 NERCs, the Parliament had also pushed for binding targets for the intermediate year 2025. The Commission’s proposal included only indicative (i.e. non-binding) targets for that year. Here, member states succeeded in watering down even the already weak Commission proposal, so that now there are only vague guiding figures for 2025.

Commenting on the outcome, Louise Duprez, senior air quality policy officer at the EEB, said: “EU action to cut air pollution is welcome and will help Europeans breathe more easily. But all in all this is a missed opportunity that will still leave tens of thousands of citizens exposed to avoidable air pollution. The Parliament and the Commission were defeated by member states, including the UK, France, Italy, Poland, Romania and Bulgaria, which preferred to allow industry and agriculture to carry on polluting rather than focusing attention on measures to save people’s lives.”

On 12 July, the Parliament ’s environment committee voted to support the provisional NEC deal, with 43 votes in favour and 14 against. Before it comes into force, the NEC proposal will go to the Parliament for a vote in plenary in November, and after that the Council will need to officially endorse the text.

Christer Ågren

Table: Country-by-country national emission reduction commitments (NERC) for 2030 in per cent as compared to the base year 2005. Left column shows the Commission’s proposal, as adjusted in early 2015; Right column shows the final outcome, as agreed on 30 June 2016.

Table: Country-by-country national emission reduction commitments (NERC) for 2030 in per cent as compared to the base year 2005. Left column shows the Commission’s proposal, as adjusted in early 2015; Right column shows the final outcome, as agreed on 30 June 2016.

Hong Kong air pollution still far exceeds WHO levels and worsening, concern group finds

Traffic congestion, spurred by growing number of private cars, is blamed for poor air quality

Concentrations of nitrogen oxides in the air in Hong Kong have consistently surpassed maximum safe levels set by the World Health Organisation [1] in the last five years, with average roadside emissions in Central, Causeway Bay and Mong Kok nearly 2.5 times higher, according to a mid-year review by a concern group.

The Clean Air Network [2] believes the source of such persistent roadside NOx pollution is traffic congestion spurred by uncontrolled growth in the number of private cars – at least 4.6 per cent per year – in the last decade.

For air measured at ambient monitoring stations, NOx levels were highest in Sham Shui Po, Kwai Chung and Tsuen Wan, all of which recorded annual average concentrations of more than 60 micrograms per cubic metre, far in excess of the WHO’s recommended level of 40.

Patrick Fung Kin-wai, the group’s chief executive, said chronically high levels of pollution were posing a significant threat to public health. He urged the government to address the threat when it formulated its planning and transportation policies.

“Roadside air quality has never been at a healthy level,” Fung said. “The public health impacts such as doctors visits and premature deaths need to be looked at.”

The group cited data from the Hedley Environmental Index [3], which estimates there were 821 pollution-related premature deaths in the first half of the year.

The same three stations also recorded average sulphur dioxide concentrations far higher than the citywide five-year average of 10mg, largely from shipping emissions stemming from the cargo terminal in Kwai Chung, but also because of power plants.

The five-year average concentration for particulate pollution smaller than 10 microns, or PM10, was highest in Tuen Mun, Central and Western, and Kwun Tong, all of which exceeded the citywide average of 38mg. The former two also beat the city’s 25mg five-year average for PM2.5, and were joined by Kwai Chung.

“Most pollution is concentrated in the western part of Hong Kong such as Kowloon West and New Territories West,” Fung said.

He recommended policies that encourage behavioural changes such as electronic road pricing and low emissions streets, as well as tighter fuel requirements for ocean vessels.

The Environmental Protection Department said there had been a clear downward trend in emissions over the last five years, which showed emissions reduction measures were paying off.

Source URL:

Finland: 1,600 early deaths every year due to air pollution

Air pollution is estimated to cause some 1,600 premature deaths in Finland every year, says a new report from the Environment Ministry. Deaths caused by air pollution shorten the lifetime of the individuals by an average of 16 years.

Taken across the entire population, this means that the life expectancy of Finns is shortened by an average of over five months due to air pollution.

Most of the health damage is caused by tiny particles (PM) or by nitrogen oxides.

About half of the PM concentrations in Finland emanates from emissions from outside the country, while the other half comes from domestic emission sources, primarily from small-scale wood burning (46%), other energy production (16%), traffic exhaust gases (12%), street dust (10%), peat production (9%), and industry (7%).

Source: Environment ministry press release, 13 April 2016