black carbon

Electric trains are healthier

May 7, 2025 By EarthWise Leave a Comment

The majority of commuter trains in the U.S. are powered by diesel fuel. This is despite the fact that electric trains are quieter, more reliable, and produce fewer greenhouse gases than diesel locomotives. A new study has found that electric trains are healthier for passengers as well.

Caltrain carries millions of passengers a year along a 47-mile route between San Francisco and San Jose. It is the busiest commuter rail system in the western U.S. Over a six-week period beginning in August 2024, Caltrain retired all 29 of its diesel locomotives and replaced them with electric trains.

As the process began, an environmental engineering and environmental health professor at UC Berkeley noticed the rapid change in the air aboard the trains and decided to study its potential health impacts. With the support of Caltrain, he installed black carbon detectors aboard the trains and tracked the improvements in air quality as old diesel locomotives were being replaced by new electric trains.

Statistical analysis of the reduction in black carbon exposure achieved by the change predicted a reduction in excess cancer deaths by 51 per million people for passengers and 330 per million people for train conductors. EPA policy states that any exposure that increases the average individual’s cancer risk by more than one per million is considered unacceptable.

In the context of the whole U.S. where millions of people commute by rail every day, the study predicts that hundreds of cases of cancer could be prevented each year. California has long-term plans to electrify most of its rail systems. The study indicates that the process shouldn’t be carried over the next 25 years but rather be sped up.

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Electric trains are quieter, more reliable than diesel. New study finds they’re healthier, too.

Photo, posted September 4, 2024, courtesy of J. Kehoe via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Wildfires and air quality

January 1, 2024 By EarthWise Leave a Comment

The wildfires last summer in parts of the U.S. and Canada fouled the air over much of the country. Air quality in many places was dangerous for human health. And such fires are becoming more numerous and more intense.

A new study by the University of Iowa has assessed the effects of two decades of wildfires on air quality and human health in the continental U.S.

From 2000 to 2020, air quality in the western U.S. has gotten worse as a result of the numerous fires in that region. More generally, all those fires have undermined the success of federal efforts to improve air quality, primarily through the reductions in automobile emissions.

American air had been getting cleaner and clearer as a result of EPA regulations on vehicle emissions, but the surge in wildfires has limited and, in some cases, erased these air quality gains. Twenty years of efforts by the EPA to make our air cleaner have been lost in fire-prone areas and in many downwind areas.

The Iowa study looked at the concentration of black carbon, a fine-particle air pollutant from fires linked to respiratory and heart disease. In the western U.S., black carbon concentrations have risen 86% on an annual basis.

Fires have also affected the air in the Midwest, although not to the same degree as in the west. The eastern U.S. had no major declines in air quality during the 2000-2020 time period. Given the episodes of smoke from Canadian wildfires experienced by the east coast this past summer – as far south as Florida – even the air in that part of the country is suffering from the spread of wildfires.

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Wildfires have erased two decades’ worth of air quality gains in western US

Photo, posted June 8, 2023, courtesy of Anthony Quintano via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Wildfires And Air Quality | Earth Wise

October 26, 2023 By EarthWise Leave a Comment

People in the Northeast have been dealing with unhealthy air quality in recent times because of smoke from hundreds of wildfires in Canada. Canada has experienced a much higher than average incidence of blazes this year with nearly 500 fires burning uncontrolled at times.

It turns out that states far away from Canada aren’t necessarily free from the impact of the fires. Early in October, smoke from a wildfire burning in Quebec made its way south all the way down to Florida and created unhealthy air quality and reduced visibility across much of the state. Smoke from the same fire had created hazy air in Boston, New York City, and parts of Connecticut before heading south.

It took a rather unusual set of atmospheric conditions to make this happen. The smoke drifted from Canada into the western Atlantic. From there, it got trapped behind a cold front and was then pushed south along the east coast until it finally moved inland across Florida.

Wildfires produce a variety of particles and gases from the burning of vegetation such as organic carbon, black carbon, nitrogen oxides, carbon monoxide and hazardous air pollutants. The mixture of particles and gases in wildfire smoke is associated with respiratory symptoms like shortness of breath and reduced lung function, as well as dangerous cardiovascular effects.

Smoke from increasingly frequent and increasingly large fires has started to undo decades of gains in air quality brought about by air pollution policies. According to researchers, wildfires in the United States in recent years have undone about 25% of past progress in cleaning up air pollution in states from coast to coast.

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Wildfire Smoke From Canada Creates Unhealthy Air Quality in Florida

Photo, posted June 8, 2023, courtesy of Anthony Quintano via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Space Tourism And The Climate | Earth Wise

July 29, 2022 By EarthWise Leave a Comment

Space tourism is human space travel for recreational purposes. A few well-known billionaires have taken rocket rides in recent years and at least a dozen companies are at the vanguard of what they are expecting to be a burgeoning industry. If space tourism truly takes off – pun intended – it could be a serious threat to the climate and the environment.

Black carbon – essentially soot – is emitted when fossil fuels, including rocket fuels, are burned. Black carbon absorbs light from the sun and releases thermal energy, making it a powerful climate warming agent. At lower altitudes, black carbon quickly falls from the sky, remaining in the atmosphere for only a matter of days or weeks.

Rockets are another story entirely. They dump black carbon into the stratosphere as they blast into space, and up there black carbon is 500 times worse for the climate and sticks around for several years.

A detailed study by researchers at University College London looked at the climate impact of present-day space launches compared with the potential massive expansion of launches from a large space tourism industry.

The overall result is that current space launches are not a significant source of emissions, but space launches would become incredibly significant if projections of tourist space flights proved to be true. Currently, there are roughly 100 space launches a year world-wide. If that number becomes thousands, the impact on the climate would be substantial.

The same researchers looked at the ozone impact of rocket launches and reached a similar conclusion. The current impact of spaceflights is not very significant, but a massive increase in launches could have a major impact on atmospheric ozone concentrations.

Space tourism may be exciting, but it also could be very dangerous for the planet.

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Space Tourism Poses a Significant ‘Risk to the Climate’

Impact of Rocket Launch and Space Debris Air Pollutant Emissions on Stratospheric Ozone and Global Climate

Photo, posted May 30, 2020, courtesy of Daniel Oberhaus (2020) via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Air Pollution Reduction And Global Warming | Earth Wise

April 13, 2021 By EarthWise Leave a Comment

The world is dealing with two serious problems affecting the atmosphere: the growing levels of carbon dioxide leading to a warming climate and the effects of air pollution on human health. It turns out that these two things are connected in complicated ways.

Countries around the world are racing to mitigate global warming by limiting carbon dioxide emissions. The combustion of fossil fuels as well as wood and other biomass produces sulfate aerosols, which are associated with acid rain as well as many human health problems. Air pollution causes an estimated seven million premature deaths per year worldwide, so reducing it is imperative.

The complication is that sulfate aerosols in the upper atmosphere actually have a cooling effect on surface air temperatures. Aerosols create bigger clouds and increase light scattering, both of which result in less sunlight reaching the surface. Large natural sources of sulfate aerosols – such as volcanic eruptions – can temporarily cool the earth until they settle out of the atmosphere.

There are many kinds and sizes of atmospheric aerosols, making predicting their effects and behavior difficult. For example, black carbon aerosols from forest fires tend to suppress cloud formation by warming the air and making tiny water droplets evaporate. However, sulfate aerosols from burning fossil fuels make clouds grow larger.

Analysis has shown that air pollution has actually reduced the amount of warming that has taken place to date. A new study by Kyushu University in Japan looked at the long-term climate effects of reductions in sulfate aerosols. The loss of cooling effect from light-scattering aerosols as emissions are reduced is a factor that cannot be ignored.

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Air pollutant reductions could enhance global warming without greenhouse gas cuts

Photo, posted January 23, 2021, courtesy of Wutthichai Charoenburi via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Dust And Himalayan Glaciers | Earth Wise

December 14, 2020 By EarthWise Leave a Comment

Glaciers in the Himalayas have been melting and retreating, as have glaciers around the world. As is the case elsewhere, human-driven climate change is a major factor. But at the lofty heights of the Himalayas, warming temperatures are not the biggest culprit. Black carbon – released into the air by burning fossil fuels or biomass such as plants, trees, and shrubs – darkens the snow and causes it to absorb more of the sun’s heat. A recent study by an international team of scientist has identified another important factor: dust.

An estimated 5 billion tons of desert dust enters the Earth’s atmosphere every year. Dust from places like Saudi Arabia gets picked up by spring winds and gets deposited on the western sides of mountains, where it can make the air 10 times more polluted than most European cities. Dust blows across industrial and desert areas in the Indian subcontinent and the Middle East and lands in the Himalayas. According to the new study, this dust is often the dominant cause of snow melt in those areas.

Desert dust causes snow melt in the same way that black carbon does. Dirty snow absorbs sunlight more easily than clean snow.

Desert dust is a natural part of Earth’s systems, but the amount of it in the atmosphere has steadily increased since the Industrial Revolution, when humans greatly expanded into desert areas and broke through surface crust that held large amounts of dust in place.

There is not much we can do about desert dust, short of eliminating deserts. But the disappearance of the Himalayan ice pack – which sustains over a billion people – can be mitigated by reducing greenhouse gas emissions to address climate change .

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Himalayan glaciers melting because of high-altitude dust

Photo, posted March 13, 2018, courtesy of Sarunas Burdulis via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Air Pollution And Bone Health | Earth Wise

February 5, 2020 By EarthWise Leave a Comment

Many of the negative effects of air pollution are well documented. Studies have shown that exposure to air pollution is associated with an increased risk of lung cancer, stroke, respiratory and cardiovascular diseases, and so on.

Now, according to a new study in India led by the Barcelona Institute for Global Health (ISGlobal), exposure to air pollution is also associated with a higher risk of developing osteoporosis. Osteoporosis, which literally means porous bone, is a disease in which the density and quality of bone is reduced. As bones become more porous and fragile, the risk of fracture is greatly increased.

The study, which surveyed 3,700 people from 28 villages in southern India, was recently published in the medical journal Jama Network Open.

The researchers used a model to estimate air pollution by fine particulate matter (commonly referred to as PM2.5) and black carbon at each participant’s residence. The research team then assessed bone health using a special type of radiography (called dual-energy x-ray absorptiometry) that measures bone density. They measured bone mass of the participants’ left hip and at the lumbar spine.

The results showed that exposure to air pollution, particularly fine particulate matter, was associated with lower levels of bone mass. Annual average exposure to PM2.5 was 32.8 micrograms per cubic meter, well above the maximum levels recommended by the World Health Organization (10 micrograms per cubic meter) and the U.S. EPA (12 micrograms per cubic meter).

The researchers say their findings add to a growing body of evidence that indicates that particulate air pollution is relevant for bone health.

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Air pollution can worsen bone health

Photo, posted November 15, 2019, courtesy of Ninara via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Algae And The Greenland Ice Sheet

February 2, 2018 By EarthWise Leave a Comment

The Greenland Ice Sheet is the second largest ice body in the world, after the Antarctic ice sheet. It is about 1,500 miles long, nearly 900 miles across at its widest point, and averages more than a mile in thickness. It has experienced record melting in recent years and is a source of great concern as the climate continues to warm. The Greenland Ice Sheet is losing an estimated 270 billion tons of ice each year. If the entire sheet were to melt, global sea levels would rise by 24 feet which, of course, would be a world-wide catastrophe.