Clear The Air News Blog Rotating Header Image


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:

OECD warns of rising costs of air pollution

Outdoor air pollution could cause up to nine million premature deaths a year by 2060 and cost US$ 3.3 trillion annually as a result of sick days, healthcare expenditure and reduced agricultural output, unless action is taken.

In 2010, outdoor air pollution caused more than three million premature deaths worldwide, with elderly people and children most vulnerable. New projections presented in an OECD report “The Economic Consequences of Outdoor Air Pollution” imply a doubling, or even tripling, of premature deaths from particulate matter (PM2.5) and ozone (O3) – or one premature death every four or five seconds – by 2060.

The projected increase in concentrations of PM2.5 and ozone will result in significant economic costs to society. The direct market impact of air pollution in terms of lower worker productivity due to illness, higher spending on health care, and lower crop yields, could exceed US$ 3,000 billion annually by 2060, equal to one per cent of GDP. For example, between now and 2060, the number of annual work days lost to air-pollution-related illness is expected to jump from 1.2 to 3.7 billion.

These estimates of economic market impacts do not however reflect the true costs of air pollution because shortening of people’s lives and pain and suffering from respiratory and cardiovascular diseases do not really have a market price. The OECD has therefore also estimated the non-market welfare costs by using economic studies on how people value their health and how much they would be prepared to pay to reduce the health risks, i.e. by introducing policies and measures that would cut air pollutant emissions.

Based on this data, the current (2015) annual global welfare costs of mortality and morbidity from outdoor air pollution are estimated at US$ 3,440 billion, and by 2060 they would amount to between US$ 20,000 and 27,000 billion a year (see table).

Table: Total global welfare costs of air pollution (billions US$)


It should be noted that air pollution damage to ecosystems, biodiversity and our cultural heritage has not been assigned any monetary value and is therefore not included in these economic estimates.

According to the projections, the biggest rises in air pollution mortality rates are expected in India, China, Korea and Central Asian countries, where rising populations and congested cities mean more people are exposed to high levels of pollution. The premature death rates are forecast to be up to three times higher in 2060 than in 2010 in China and up to four times higher in India. Mortality rates are however seen to be stabilising in the United States and falling in much of Western Europe thanks in part to efforts to move to cleaner energy and transport.

Projected GDP losses will be biggest in China, Russia, India, Korea and countries in Eastern Europe and the Caspian region, as health costs and lower labour productivity hit output.

“The number of lives cut short by air pollution is already terrible and the potential rise in the next few decades is terrifying,” said OECD Environment Director Simon Upton. “If this is not motivation enough to act, this report shows there will also be a heavy economic cost to not taking action. We must prevent these projections from becoming reality.”

“It is time for governments to stop fussing about the costs of efforts to limit air pollution and start worrying about the much larger costs of allowing it to continue unchecked. Their citizens’ lives are in their hands,” concluded Simon Upton.

Christer Ågren

‘Healing’ detected in Antarctic ozone hole

Researchers say they have found the first clear evidence that the thinning in the ozone layer above Antarctica is starting to heal.

The scientists said that in September 2015 the hole was around 4 million sq km smaller than it was in the year 2000 – an area roughly the size of India.

The gains have been credited to the long term phasing out of ozone-destroying chemicals.

The study also sheds new light on the role of volcanoes in making the problem worse.

Skin cancer worry

British scientists first noticed a dramatic thinning of ozone in the stratosphere some 10 kilometres above Antarctica in the mid 1980s.

Ozone is important because it blocks out harmful ultraviolet radiation from the Sun.

Its absence increases the chances of skin cancer, cataract damage, and harm to animals and plants.

In 1986, US researcher Susan Solomon showed that ozone was being destroyed by the presence of molecules containing chlorine and bromine that came from chlorofluorocarbons (CFCs). These gases were found in everything from hairsprays to refrigerators to air conditioning units.

The reason the thinning was occurring mainly over Antarctica was because of the extreme cold and large amounts of light. These helped produce what are termed Polar Stratospheric Clouds.

In these chilled-out clouds, the chlorine chemistry occurs that destroys the ozone.

Thanks to the global ban on the use of CFCs in the Montreal Protocol in 1987, the situation in Antarctica has been slowly improving.

Several studies have shown the declining influence of CFCs, but according to the authors this new study shows the “first fingerprints of healing” and the ozone layer is actively growing again.

Prof Solomon and colleagues carried out detailed measurements of the amount of ozone in the stratosphere between 2000 and 2015.

Using data from weather balloons, satellites and model simulations, they were able to show that the thinning of the layer had declined by 4 million sq km over the period.

The found that more than half the shrinkage was due solely to the reduction in atmospheric chlorine.

Normally measurements are taken in October when the ozone hole is at its largest. But this team believed they would get a better picture by looking at readings taken in September, when temperatures are still low but other factors that can influence the amount of ozone, such as the weather, are less prevalent.

“Even though we phased out the production of CFCs in all countries including India and China around the year 2000, there’s still a lot of chlorine left in the atmosphere,” Prof Solomon told the BBC World Service Science in Action programme.

“It has a lifetime of about 50-100 years, so it is starting to slowly decay and the ozone will slowly recover.

“We don’t expect to see a complete recovery until about 2050 or 2060 but we are starting to see that in September the ozone hole is not as bad as it used to be.”

One finding that puzzled researchers was the October 2015 reading that showed the biggest ozone hole on record over Antarctica.

The scientists believe that a key contributor to the record hole was volcanic activity.

“After an eruption, volcanic sulphur forms tiny particles and those are the seeds for Polar Stratospheric Clouds,” Prof Solomon told Science in Action.

“You get even more of these clouds when you have a recent major volcanic eruption and that leads to additional ozone loss.”

“Until we did our recent work no-one realised that the Calbuco eruption in Chile, actually had significantly affected the ozone loss in October of last year.”

The study has been hailed as “historically significant” by some other researchers in the field.

“This is the first convincing evidence that the healing of the Antarctic ozone hole has now started,” said Dr Markus Rex from the Alfred Wegener Institute for Polar and Marine Research in Germany.

“Right now the state of the ozone layer is still really bad, but I find it very important that we know the Montreal Protocol is working and has an effect on the size of the hole and that is a big step forward.”

Differing views

However others are not entirely convinced that the decline shown in the new study is down to a reduction in the amount of chlorine in the stratosphere.

“The data clearly show significant year to year variations that are much greater than the inferred trends shown in the paper,” said Dr Paul Newman from Nasa.

“If the paper included this past year, which had a much more significant ozone hole due to lower wave driven forcing, the overall trend would be less.”

Regardless of these questions, the scientists involved in the study believe the ozone story is a great role model for how to tackle global environmental problems.

“It’s just been remarkable,” said Prof Solomon.

“This was an era in which international co-operation went rather well on some issues. I was inspired by the way the developed and developing countries were able to work together on dealing with the ozone hole,” said Prof Solomon.

Hong Kong sees bigger rise in poisonous ozone pollution than industrial Guangdong

Elizabeth Cheung

But environmental campaigners say pollution cannot be solely blamed on mainland sources

Hong Kong has seen a bigger rise in poisonous ozone pollution than industrial Guangdong – but pollutants from the mainland are not solely to blame, environmental campaigners say.

Environmentalists from Clean Air Network have urged the government to take tougher action on air pollutants through transport planning measures.

Campaigners looked at the data on ozone levels from the Guangdong-Hong Kong-Macau air quality monitoring database. Ozone levels recorded at the 13 monitoring stations in Guangdong province saw a 6.1 per cent increase between 2010 and 2014, compared to the 9.2 per cent increase recorded at the three Hong Kong stations, set up in Tsuen Wan, Tap Mun and Tung Chung.

When data from local general air quality monitoring stations was studied, excluding three included in a regional monitoring scheme, the rise in the level of ozone was even greater, at 17.1 per cent.
Between 2006 and 2014, local stations recorded a 27.2 per cent rise in ozone, in contrast to 19.5 per cent in the neighbouring province.

The Environmental Protection Department said more easterly prevailing winds from the mainland explained greater air pollution in eastern parts of the city, but Clean Air Network said local factors still played a role.

Kwun Tong in Kowloon East experienced a drop in the number of hours defined as having experienced serious pollution between 1992 and 2014 despite its largely northeasterly winds.

“The high level of ozone is not solely a regional issue. We can target ozone pollution both locally and regionally,” said Kwong Sum-yin, chief executive officer of the group.

Hong Kong and Guangdong have set up joint emissions reduction targets, which include four pollutants, two of which are the main sources of ozone production. But the group urged authorities to include targets on ozone.

Locally, Kwong said the rise in the number of vehicles on the roads over the past decade had contributed to the deteriorating air pollution in the city. Between 2005 and 2014, the number of trips by vehicles through the three cross-harbour tunnels daily increased from 228,000 to more than 250,000. Meanwhile, nitrogen dioxide, one of the key air pollutants measured at four roadside stations, increased steadily until 2013.

Kwong said people in Hong Kong were still exposed to significant health risks from air pollution. According to the Hedley index, an indicator developed by the University of Hong Kong’s public health school to show the public health costs and risks from pollution, as many as 2,196 people died prematurely last year due to air pollution. The cost to the public purse of such health problems amounted to HK$27 billion.

“Although there was a slight improvement in air quality, the health of people could not be guaranteed,” she said.

Source URL:

Harmful ozone levels in Hong Kong up 35pc in last 15 years

Concentrations of ozone in the city’s air have increased by a third in the last 15 years, highlighting yet again the severity in regional air pollution, according to government data.

Between 1999 and last year, concentrations of ambient ozone at the city’s general air quality monitoring stations rose by 35 per cent, despite levels of all other pollutants showing decreases.

Preliminary data released by the Environmental Protection Department today recorded ozone concentrations at general stations increasing by 7 per cent from 43 micrograms per cubic metre to 46 micrograms per cubic metre last year.

“This once again shows more needs to be done in terms of cooperation with the region,” said Mok Kwai-cheung, the department’s assistant director of environmental protection.

Ozone is a major component of photochemical smog that reduces visibility and threatens human health when exposure is prolonged and high.

The pollutant is formed by a reaction between volatile organic compounds (VOCs) and nitrogen oxide (NOx) generated from other combustion sources. The dirty, orange smog enveloping views of the harbour on heavily polluted days is created when these two pollutants react with sunlight.

Hong Kong has set a target to reduce NOx by 20 to 30 per cent and VOCs by 15 per cent by 2020 in accordance with a regional air quality management plan between the city and Guangdong.

A cross-border study funded by the department last year found that nearly half of the ambient VOC levels in the Pearl River Delta region were traffic-related, with petrol exhaust the biggest single contributor.

The report suggested that reducing traffic in the delta region by half could be one of the most effective means of combatting regional smog. But cutting VOC emissions from traffic by half could achieve the same effect.
Source URL (modified on Feb 24th 2015, 6:52pm):