Tag Archives: Ozone

Ozone loss may have caused mass extinction

The loss of ozone may have caused the extinction many millions of years ago of most life on Earth, scientists believe.

LONDON, 21 February, 2018 – Californian scientists have found a new way to account for extinction and to explain mass murder on a planetary scale.

Seven out of 10 land animals perished at the end of the Permian, 252 million years ago. So did 95% of marine species. And the deadly factor at work may have been the destruction of atmospheric ozone, the protective screen in the stratosphere that eliminates harmful ultraviolet light.

Jeffrey Benca of the University of California Berkeley and colleagues report in the journal Science Advances that they irradiated a series of dwarf pines with doses of ultraviolet-B radiation up to 13 times stronger than any on Earth today.

They used 60 pines of the species Pinus mugo, irradiated them for 56 days, and then spent three years examining 57,000 pollen grains produced over that period.

UV-B wavelengths are associated with mutations in DNA, the inheritance mechanism of all life on Earth. The dose chosen was the one to which creatures might have been exposed at the close of the Permian period, an episode characterised by immense volcanic eruptions that would have damaged the upper atmosphere.

Exposed to sterility

And, the researchers found, after two months exposure, the trees survived, but at a cost: they had become sterile. Their cones shrivelled within days of emerging. Once restored to present day, open air conditions, the pines all recovered.

Plants underwrite all animal life: repeated bouts of forest sterility could, researchers think, have played a role in the collapse of the planet’s biosphere.

Research like this is at the heart of climate science: it is a tenet of earth sciences that the present is key to the past. So it follows that what happened in the past could be relevant to the present.

And since biologists have argued that the double punch of habitat destruction and climate change could be precipitating a sixth great extinction, there has always been intense interest in the triggers of the previous five. So far, no other bout of extinction has been on the scale that occurred at the end of the Permian.

“The slowly unfolding extinction on land over maybe tens or hundreds of thousands of years may have been caused by reproductive troubles at the base of the food chain”

That doesn’t mean the latest study has identified the smoking gun: it does, however, add immediacy to new concerns about the present state of the ozone layer.

Even before the first evidence that global warming had already begun, British and US scientists confirmed that human action – in the release of a suite of industrially-important gases called chlorofluorocarbons – had begun to erode the invisible shield of stratospheric ozone that has always sheltered life on Earth.

In a prompt response 30 years ago, the world’s nations banned the use of such gases. Concerted action on the other contemporary alarm, about global warming, has been more difficult to achieve.

Ozone however is not the only suspect in the search for the Permian mass murder mechanisms. Other researchers have already suggested that high atmospheric carbon dioxide levels, driven by enormous, slow volcanic eruptions, could have turned the oceans increasingly acidic.

Dependent on plants

Biologists may never arrive at clinching evidence from the scene of a crime that happened even before the first dinosaurs colonised the planet. And, since the Permian extinction took place over a 500,000-year period, there may be no single murder weapon.

Such studies, once again, illuminate the intricate dependence of all animals on plant life, and all plant life on atmospheric conditions. The research has potent lessons for those already concerned about worldwide forest loss, so far largely due to human action.

“Paleontologists have come up with various kill scenarios for mass extinctions, but plant life may not be affected by dying suddenly as much as through interrupting one part of the life cycle, such as reproduction, over a long period of time, causing the population to dwindle and potentially disappear,” said Cindy Looy, an integrative biologist at Berkeley, and a co-author.

And a third author, Ivo Duijnstee, from the same research team, said: “Jeff, who used his plant growth chambers as a time machine to test the potential of a hypothesis about what may have happened 252 million years ago, provides an excellent example illustrating how the slowly unfolding extinction on land over maybe tens or hundreds of thousands of years may have been caused by reproductive troubles at the base of the food chain.” – Climate News Network

The loss of ozone may have caused the extinction many millions of years ago of most life on Earth, scientists believe.

LONDON, 21 February, 2018 – Californian scientists have found a new way to account for extinction and to explain mass murder on a planetary scale.

Seven out of 10 land animals perished at the end of the Permian, 252 million years ago. So did 95% of marine species. And the deadly factor at work may have been the destruction of atmospheric ozone, the protective screen in the stratosphere that eliminates harmful ultraviolet light.

Jeffrey Benca of the University of California Berkeley and colleagues report in the journal Science Advances that they irradiated a series of dwarf pines with doses of ultraviolet-B radiation up to 13 times stronger than any on Earth today.

They used 60 pines of the species Pinus mugo, irradiated them for 56 days, and then spent three years examining 57,000 pollen grains produced over that period.

UV-B wavelengths are associated with mutations in DNA, the inheritance mechanism of all life on Earth. The dose chosen was the one to which creatures might have been exposed at the close of the Permian period, an episode characterised by immense volcanic eruptions that would have damaged the upper atmosphere.

Exposed to sterility

And, the researchers found, after two months exposure, the trees survived, but at a cost: they had become sterile. Their cones shrivelled within days of emerging. Once restored to present day, open air conditions, the pines all recovered.

Plants underwrite all animal life: repeated bouts of forest sterility could, researchers think, have played a role in the collapse of the planet’s biosphere.

Research like this is at the heart of climate science: it is a tenet of earth sciences that the present is key to the past. So it follows that what happened in the past could be relevant to the present.

And since biologists have argued that the double punch of habitat destruction and climate change could be precipitating a sixth great extinction, there has always been intense interest in the triggers of the previous five. So far, no other bout of extinction has been on the scale that occurred at the end of the Permian.

“The slowly unfolding extinction on land over maybe tens or hundreds of thousands of years may have been caused by reproductive troubles at the base of the food chain”

That doesn’t mean the latest study has identified the smoking gun: it does, however, add immediacy to new concerns about the present state of the ozone layer.

Even before the first evidence that global warming had already begun, British and US scientists confirmed that human action – in the release of a suite of industrially-important gases called chlorofluorocarbons – had begun to erode the invisible shield of stratospheric ozone that has always sheltered life on Earth.

In a prompt response 30 years ago, the world’s nations banned the use of such gases. Concerted action on the other contemporary alarm, about global warming, has been more difficult to achieve.

Ozone however is not the only suspect in the search for the Permian mass murder mechanisms. Other researchers have already suggested that high atmospheric carbon dioxide levels, driven by enormous, slow volcanic eruptions, could have turned the oceans increasingly acidic.

Dependent on plants

Biologists may never arrive at clinching evidence from the scene of a crime that happened even before the first dinosaurs colonised the planet. And, since the Permian extinction took place over a 500,000-year period, there may be no single murder weapon.

Such studies, once again, illuminate the intricate dependence of all animals on plant life, and all plant life on atmospheric conditions. The research has potent lessons for those already concerned about worldwide forest loss, so far largely due to human action.

“Paleontologists have come up with various kill scenarios for mass extinctions, but plant life may not be affected by dying suddenly as much as through interrupting one part of the life cycle, such as reproduction, over a long period of time, causing the population to dwindle and potentially disappear,” said Cindy Looy, an integrative biologist at Berkeley, and a co-author.

And a third author, Ivo Duijnstee, from the same research team, said: “Jeff, who used his plant growth chambers as a time machine to test the potential of a hypothesis about what may have happened 252 million years ago, provides an excellent example illustrating how the slowly unfolding extinction on land over maybe tens or hundreds of thousands of years may have been caused by reproductive troubles at the base of the food chain.” – Climate News Network

Ozone layer recovery falters unexpectedly

The recovery of the damaged ozone layer which protects life on Earth from harmful solar radiation is no longer happening worldwide.

LONDON, 6 February, 2018 – The Earth’s protective ozone layer is not recovering uniformly from the damage caused to it by industry and other human activities. And scientists are not sure why it isn’t.

An international research team says the ozone, which protects humans and other species from harmful ultraviolet radiation, is continuing to recover at the poles. But recovery at lower latitudes, where far more people live, is not.

The layer has been declining since the 1970s because of the effect of man-made chemicals, chiefly chlorofluorocarbons (CFCs) and similar gases, used mainly in refrigerants and aerosols.

There is a link between the CFCs and global warming, though they are different and neither is the main cause of the other. Some suggested CFC replacements themselves proved to be powerful greenhouse gases.

CFCs and the other gases were banned under an international agreement, the Montreal Protocol, and since then parts of the layer have been recovering, particularly at the poles.

But the latest research, published in the journal Atmospheric Chemistry and Physics, finds that the bottom part of the ozone layer at more populated latitudes is not recovering, for reasons so far unidentified.

Radiation blocker

Ozone forms in the stratosphere, between about 10 and 50 km above the Earth and above the troposphere where terrestrial species live. Much of it is in the lower part of the stratosphere, where it absorbs UV radiation from the Sun which can damage DNA in plants, animals and humans if it reaches the Earth’s surface.

So the discovery in the 1970s that CFCs were destroying the ozone and causing the Antarctic ozone “hole” sparked rare international co-operation to solve the problem.

The outcome was the 1987 Montreal Protocol, the phase-out of CFCs, and, recently, the first signs of recovery in the Antarctic. The upper stratosphere at lower latitudes is also showing clear signs of recovery.

But scientists have now found that stratospheric ozone is probably not recovering at lower latitudes, between 60⁰N and 60⁰S (London lies at 51⁰N), because of unexpected decreases in ozone in the lower part of the stratosphere.

Jonathan Shanklin, one of the British Antarctic Survey (BAS) scientists who discovered the ozone hole in 1985, told the Climate News Network from the BAS Halley research station where he is working now:

“The problem and consequences of ozone depletion are not yet over”

“…This new research is interesting and provides a novel perspective on changes in the ozone layer. It shows that even in an area of science that is fairly well understood there are still surprises in the fine detail.

“It is clear from Antarctic data that the ozone layer is beginning to recover where it was worst affected, though it will take many more decades before it is back to its condition of the 1970s.

“Although significant ozone depletion mostly affects the Antarctic, conditions in the ozone layer over the Arctic are sometimes sufficient to create substantial depletion. That is the case this year and at the moment there is significant ozone depletion over northern Ireland and Scotland.  The problem and consequences of ozone depletion are not yet over.”

Dr Anna Jones, senior tropospheric chemist at BAS, said: “We do not yet understand what’s causing the decline. To enable predictions of future ozone amounts, and to identify whether (and what) action might be needed to prevent further decreases, it is extremely important to understand what is causing the observed downward trend.”

Professor Joanna Haigh, co-director of the Grantham Institute for Climate Change and the Environment at Imperial College London, is co-author of the study. She said ozone had been declining seriously since the 1980s, but while the banning of CFCs was leading to a recovery at the poles, this did not appear to be true for the lower latitudes.

Greater risk

“The potential for harm in lower latitudes may actually be worse than at the poles,” she said. “The decreases in ozone are less than we saw at the poles before the Montreal Protocol was enacted, but UV radiation is more intense in these regions and more people live there.”

Although they’re not certain what’s causing this decline, the authors suggest two possibilities. One is that climate change is altering the pattern of atmospheric circulation, causing more ozone to be carried away from the tropics.

The other is that very short-lived substances (VSLSs), which contain chlorine and bromine, could be destroying ozone in the lower stratosphere. VSLSs include chemicals used as solvents, paint strippers, and as degreasing agents. One is even used in the production of an ozone-friendly replacement for CFCs.

Scientists had thought that VSLSs would not persist long enough in the atmosphere to reach the stratosphere and affect ozone. But Dr William Ball from ETH Zurich, who led the analysis, said: “The finding of declining low-latitude ozone is surprising, since our current best atmospheric circulation models do not predict this effect. Very short-lived substances could be the missing factor in these models.”

The study was the work of researchers from Switzerland, the UK, the US, Sweden, Canada and Finland, and included data from satellite missions, including by NASA. – Climate News Network

The recovery of the damaged ozone layer which protects life on Earth from harmful solar radiation is no longer happening worldwide.

LONDON, 6 February, 2018 – The Earth’s protective ozone layer is not recovering uniformly from the damage caused to it by industry and other human activities. And scientists are not sure why it isn’t.

An international research team says the ozone, which protects humans and other species from harmful ultraviolet radiation, is continuing to recover at the poles. But recovery at lower latitudes, where far more people live, is not.

The layer has been declining since the 1970s because of the effect of man-made chemicals, chiefly chlorofluorocarbons (CFCs) and similar gases, used mainly in refrigerants and aerosols.

There is a link between the CFCs and global warming, though they are different and neither is the main cause of the other. Some suggested CFC replacements themselves proved to be powerful greenhouse gases.

CFCs and the other gases were banned under an international agreement, the Montreal Protocol, and since then parts of the layer have been recovering, particularly at the poles.

But the latest research, published in the journal Atmospheric Chemistry and Physics, finds that the bottom part of the ozone layer at more populated latitudes is not recovering, for reasons so far unidentified.

Radiation blocker

Ozone forms in the stratosphere, between about 10 and 50 km above the Earth and above the troposphere where terrestrial species live. Much of it is in the lower part of the stratosphere, where it absorbs UV radiation from the Sun which can damage DNA in plants, animals and humans if it reaches the Earth’s surface.

So the discovery in the 1970s that CFCs were destroying the ozone and causing the Antarctic ozone “hole” sparked rare international co-operation to solve the problem.

The outcome was the 1987 Montreal Protocol, the phase-out of CFCs, and, recently, the first signs of recovery in the Antarctic. The upper stratosphere at lower latitudes is also showing clear signs of recovery.

But scientists have now found that stratospheric ozone is probably not recovering at lower latitudes, between 60⁰N and 60⁰S (London lies at 51⁰N), because of unexpected decreases in ozone in the lower part of the stratosphere.

Jonathan Shanklin, one of the British Antarctic Survey (BAS) scientists who discovered the ozone hole in 1985, told the Climate News Network from the BAS Halley research station where he is working now:

“The problem and consequences of ozone depletion are not yet over”

“…This new research is interesting and provides a novel perspective on changes in the ozone layer. It shows that even in an area of science that is fairly well understood there are still surprises in the fine detail.

“It is clear from Antarctic data that the ozone layer is beginning to recover where it was worst affected, though it will take many more decades before it is back to its condition of the 1970s.

“Although significant ozone depletion mostly affects the Antarctic, conditions in the ozone layer over the Arctic are sometimes sufficient to create substantial depletion. That is the case this year and at the moment there is significant ozone depletion over northern Ireland and Scotland.  The problem and consequences of ozone depletion are not yet over.”

Dr Anna Jones, senior tropospheric chemist at BAS, said: “We do not yet understand what’s causing the decline. To enable predictions of future ozone amounts, and to identify whether (and what) action might be needed to prevent further decreases, it is extremely important to understand what is causing the observed downward trend.”

Professor Joanna Haigh, co-director of the Grantham Institute for Climate Change and the Environment at Imperial College London, is co-author of the study. She said ozone had been declining seriously since the 1980s, but while the banning of CFCs was leading to a recovery at the poles, this did not appear to be true for the lower latitudes.

Greater risk

“The potential for harm in lower latitudes may actually be worse than at the poles,” she said. “The decreases in ozone are less than we saw at the poles before the Montreal Protocol was enacted, but UV radiation is more intense in these regions and more people live there.”

Although they’re not certain what’s causing this decline, the authors suggest two possibilities. One is that climate change is altering the pattern of atmospheric circulation, causing more ozone to be carried away from the tropics.

The other is that very short-lived substances (VSLSs), which contain chlorine and bromine, could be destroying ozone in the lower stratosphere. VSLSs include chemicals used as solvents, paint strippers, and as degreasing agents. One is even used in the production of an ozone-friendly replacement for CFCs.

Scientists had thought that VSLSs would not persist long enough in the atmosphere to reach the stratosphere and affect ozone. But Dr William Ball from ETH Zurich, who led the analysis, said: “The finding of declining low-latitude ozone is surprising, since our current best atmospheric circulation models do not predict this effect. Very short-lived substances could be the missing factor in these models.”

The study was the work of researchers from Switzerland, the UK, the US, Sweden, Canada and Finland, and included data from satellite missions, including by NASA. – Climate News Network

Trans-Pacific flights harm climate most

FOR IMMEDIATE RELEASE Scientists have found that emissions from aircraft overflying part of the Pacific are causing the highest production of ozone, a short-lived greenhouse gas. LONDON, 7 September – If you’re planning on taking a flight but you’re worried about the volume of greenhouse gas emissions your aircraft journey will cause, don’t – whatever you do – fly to or from Australia or New Zealand. A team of researchers from Massachusetts Institute of Technology (MIT) used a global chemistry/transport model to find out which parts of the world are particularly sensitive to the creation of ozone: they then investigated which individual flights created the most ozone. Results of the MIT research which are published in the journal Environmental Research Letters show that an area of the Pacific, about 1,000 km east of the Solomon Islands, is the most sensitive to aircraft emissions. The study found that in this region 1kg of aircraft emissions results in an extra 15kg of ozone being produced over a year, a figure five times higher than the sensitivity in Europe and nearly four times that in North America. But a large part of Australia, southeast Asia and an area stretching right across to Madagascar off the east cost of Africa are also rated as being highly sensitive to emissions. Ozone is a potent but short-lived greenhouse gas with comparable short-term effects to those of carbon dioxide, produced when emissions of oxides of nitrogen (NOx) – such as nitric oxide and nitrogen dioxide – interact with sunlight. Ozone’s production and destruction is therefore heavily dependent on the particular state of the atmosphere, and its effects are localised – felt in specific regions at specific times. More than 80,000 individual flights around the world were analysed. The researchers found that the 10 highest ozone-producing flights either originated in, or were destined for, New Zealand or Australia. Top of the league for the highest amount of ozone generated – 25,300 kg worth – is a flight from Sydney to Mumbai.

Detours possible

Other high-scoring flights include Sydney-Honolulu, Auckland-Seoul and Brisbane-Bangkok. Steven Barrett, the lead author of the study, told Climate News Network that the amount of ozone produced by flights alters depending on the time of the year – with the autumn period causing the most ozone pollution. “There have been many studies of the total impact of civil aviation emissions on the atmosphere but there is very little knowledge of how individual flights change the environment,” says Barrett. “The places that the sensitivities are highest now are the fastest-growing regions in terms of civil aviation growth, so there could potentially be ways to achieve significant reductions in the climate impact of aviation by focusing on re-routing aircraft around the particular regions of the world where ozone formation is highly sensitive to NOx emissions.” But while this might mean less ozone, it would mean more of another greenhouse gas being emitted into the atmosphere. “Of course, longer flights are going to burn more fuel and emit more CO2, so there will be a trade=off between increasing flight distance and other climate impacts, such as the effect of ozone,” says Barrett. “The scientific underpinning of this trade-off needs further investigation so that we have a better understanding and can see whether such a trade-off can be justified.” – Climate News Network

FOR IMMEDIATE RELEASE Scientists have found that emissions from aircraft overflying part of the Pacific are causing the highest production of ozone, a short-lived greenhouse gas. LONDON, 7 September – If you’re planning on taking a flight but you’re worried about the volume of greenhouse gas emissions your aircraft journey will cause, don’t – whatever you do – fly to or from Australia or New Zealand. A team of researchers from Massachusetts Institute of Technology (MIT) used a global chemistry/transport model to find out which parts of the world are particularly sensitive to the creation of ozone: they then investigated which individual flights created the most ozone. Results of the MIT research which are published in the journal Environmental Research Letters show that an area of the Pacific, about 1,000 km east of the Solomon Islands, is the most sensitive to aircraft emissions. The study found that in this region 1kg of aircraft emissions results in an extra 15kg of ozone being produced over a year, a figure five times higher than the sensitivity in Europe and nearly four times that in North America. But a large part of Australia, southeast Asia and an area stretching right across to Madagascar off the east cost of Africa are also rated as being highly sensitive to emissions. Ozone is a potent but short-lived greenhouse gas with comparable short-term effects to those of carbon dioxide, produced when emissions of oxides of nitrogen (NOx) – such as nitric oxide and nitrogen dioxide – interact with sunlight. Ozone’s production and destruction is therefore heavily dependent on the particular state of the atmosphere, and its effects are localised – felt in specific regions at specific times. More than 80,000 individual flights around the world were analysed. The researchers found that the 10 highest ozone-producing flights either originated in, or were destined for, New Zealand or Australia. Top of the league for the highest amount of ozone generated – 25,300 kg worth – is a flight from Sydney to Mumbai.

Detours possible

Other high-scoring flights include Sydney-Honolulu, Auckland-Seoul and Brisbane-Bangkok. Steven Barrett, the lead author of the study, told Climate News Network that the amount of ozone produced by flights alters depending on the time of the year – with the autumn period causing the most ozone pollution. “There have been many studies of the total impact of civil aviation emissions on the atmosphere but there is very little knowledge of how individual flights change the environment,” says Barrett. “The places that the sensitivities are highest now are the fastest-growing regions in terms of civil aviation growth, so there could potentially be ways to achieve significant reductions in the climate impact of aviation by focusing on re-routing aircraft around the particular regions of the world where ozone formation is highly sensitive to NOx emissions.” But while this might mean less ozone, it would mean more of another greenhouse gas being emitted into the atmosphere. “Of course, longer flights are going to burn more fuel and emit more CO2, so there will be a trade=off between increasing flight distance and other climate impacts, such as the effect of ozone,” says Barrett. “The scientific underpinning of this trade-off needs further investigation so that we have a better understanding and can see whether such a trade-off can be justified.” – Climate News Network

Plants wilt as heat increases ozone

FOR IMMEDIATE RELEASE Plants are significantly less able to absorb low-level ozone during a heatwave, researchers have found, with implications for human health. LONDON, 20 July – Rising temperatures could be bad news for people with bad lungs. Two new lines of research are bleak reminders of the link between air quality and human health. A study from the University of York in the UK reports that ozone levels soar during heat waves – perhaps because the capacity of plants to absorb ozone is curtailed as the mercury goes up. When the ground is dry and the temperatures rise, plants become stressed: they shut their stomata – those tiny pores in their leaves – to conserve moisture. It means they can survive the high ozone levels that tend to follow traffic fumes and factory exhausts in hot weather.  But it also means they cannot react to the ozone. “Vegetation can absorb as much as 20% of the global atmospheric ozone production, so the potential impact on air quality is substantial”, said Dr Lisa Emberson of the university’s Stockholm Environment Institute. She and colleagues report in the journal Atmospheric Chemistry and Physics that they studied the European heat wave of June and July 2006, and modelled the hazard to human health under conditions of both perfect and minimal ozone absorption. They calculate that the extra ozone not absorbed by plants during the heat wave – and for 16 days, levels of ozone would have been above the threshold for human safety – accounted for 460 extra deaths in the UK.

Acute effect on south-east Asia

Ozone in the stratosphere is vital to human health: it screens out dangerous wavelengths of ultraviolet light. Ozone in the lower atmosphere though is a toxin, and a dangerous irritant that can lead to increased asthma attacks and lung inflammation. Pinning individual deaths to this or that environmental cause is very difficult, but using statistical logic, epidemiologists have been comfortably calculating notional extra deaths because of air pollution for decades. Worldwide, according to a report in Environmental Research Letters, more than two million people die because of human-caused outdoor air pollution. Researchers report that, so far, climate change has had only a minimal effect on death rates. Around 470,000 people die each year because of ozone pollution, and around 2.1 million deaths are caused by fine particulate matter – tiny particles that become trapped in the lungs. Once again, the research is based on climate model simulations. Jason West of the University of North Carolina, US, one of the authors, said: “Our estimates make outdoor air pollution among the most important environmental risk factors for health. Many of these deaths are estimated to occur in East Asia and South Asia, where population is high and air pollution is severe.” – Climate News Network

FOR IMMEDIATE RELEASE Plants are significantly less able to absorb low-level ozone during a heatwave, researchers have found, with implications for human health. LONDON, 20 July – Rising temperatures could be bad news for people with bad lungs. Two new lines of research are bleak reminders of the link between air quality and human health. A study from the University of York in the UK reports that ozone levels soar during heat waves – perhaps because the capacity of plants to absorb ozone is curtailed as the mercury goes up. When the ground is dry and the temperatures rise, plants become stressed: they shut their stomata – those tiny pores in their leaves – to conserve moisture. It means they can survive the high ozone levels that tend to follow traffic fumes and factory exhausts in hot weather.  But it also means they cannot react to the ozone. “Vegetation can absorb as much as 20% of the global atmospheric ozone production, so the potential impact on air quality is substantial”, said Dr Lisa Emberson of the university’s Stockholm Environment Institute. She and colleagues report in the journal Atmospheric Chemistry and Physics that they studied the European heat wave of June and July 2006, and modelled the hazard to human health under conditions of both perfect and minimal ozone absorption. They calculate that the extra ozone not absorbed by plants during the heat wave – and for 16 days, levels of ozone would have been above the threshold for human safety – accounted for 460 extra deaths in the UK.

Acute effect on south-east Asia

Ozone in the stratosphere is vital to human health: it screens out dangerous wavelengths of ultraviolet light. Ozone in the lower atmosphere though is a toxin, and a dangerous irritant that can lead to increased asthma attacks and lung inflammation. Pinning individual deaths to this or that environmental cause is very difficult, but using statistical logic, epidemiologists have been comfortably calculating notional extra deaths because of air pollution for decades. Worldwide, according to a report in Environmental Research Letters, more than two million people die because of human-caused outdoor air pollution. Researchers report that, so far, climate change has had only a minimal effect on death rates. Around 470,000 people die each year because of ozone pollution, and around 2.1 million deaths are caused by fine particulate matter – tiny particles that become trapped in the lungs. Once again, the research is based on climate model simulations. Jason West of the University of North Carolina, US, one of the authors, said: “Our estimates make outdoor air pollution among the most important environmental risk factors for health. Many of these deaths are estimated to occur in East Asia and South Asia, where population is high and air pollution is severe.” – Climate News Network