Acid rain, ozone depletion and global warming

What is Acid rain?

Acid rain "Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.

Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other living things that rely on the water.

Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone.

Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles.

Scientists discovered, and have confirmed, that sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal.

Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of sulfuric acid and nitric acid.

The effect of acid rain

Acid deposition has a variety of effects, including damage to forests and soils, fish and other living things, materials, and human health. Acid rain also reduces how far and how clearly we can see through the air, an effect called visibility reduction. The acid rain effects section provides more details on each of these.

Ozone depletion

For over fifty years, chlorofluorocarbons (CFCs) were thought of as miracle substances. They are stable, nonflammable, low in toxicity, and inexpensive to produce. Over time, CFCs found uses as refrigerants, solvents, foam blowing agents, and in other smaller applications. Other chlorine-containing compounds include methyl chloroform, a solvent, and carbon tetrachloride, an industrial chemical. Halons, extremely effective fire extinguishing agents, and methyl bromide, an effective produce and soil fumigant, contain bromine. All of these compounds have atmospheric lifetimes long enough to allow them to be transported by winds into the stratosphere. Because they release chlorine or bromine when they break down, they damage the protective ozone layer. The discussion of the ozone depletion process below focuses on CFCs, but the basic concepts apply to all of the ozone-depleting substances (ODS).

In the early 1970s, researchers began to investigate the effects of various chemicals on the ozone layer, particularly CFCs, which contain chlorine. They also examined the potential impacts of other chlorine sources. Chlorine from swimming pools, industrial plants, sea salt, and volcanoes does not reach the stratosphere. Chlorine compounds from these sources readily combine with water and repeated measurements show that they rain out of the troposphere very quickly. In contrast, CFCs are very stable and do not dissolve in rain. Thus, there are no natural processes that remove the CFCs from the lower atmosphere. Over time, winds drive the CFCs into the stratosphere.

The CFCs are so stable that only exposure to strong UV radiation breaks them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created. To return to the analogy comparing ozone levels to a stream's depth, CFCs act as a siphon, removing water faster than normal and reducing the depth of the stream.

Large fires and certain types of marine life produce one stable form of chlorine that does reach the stratosphere. However, numerous experiments have shown that CFCs and other widely-used chemicals produce roughly 85% of the chlorine in the stratosphere, while natural sources contribute only 15%.

Large volcanic eruptions can have an indirect effect on ozone levels. Although Mt. Pinatubo's 1991 eruption did not increase stratospheric chlorine concentrations, it did produce large amounts of tiny particles called aerosols (different from consumer products also known as aerosols). These aerosols increase chlorine's effectiveness at destroying ozone. The aerosols only increased depletion because of the presence of CFC- based chlorine. In effect, the aerosols increased the efficiency of the CFC siphon, lowering ozone levels even more than would have otherwise occurred. Unlike long-term ozone depletion, however, this effect is short-lived. The aerosols from Mt. Pinatubo have already disappeared, but satellite, ground-based, and balloon data still show ozone depletion occurring closer to the historic trend.

One example of ozone depletion is the annual ozone "hole" over Antarctica that has occurred during the Antarctic Spring since the early 1980s. Rather than being a literal hole through the layer, the ozone hole is a large area of the stratosphere with extremely low amounts of ozone. Ozone levels fall by over 60% during the worst years.

In addition, research has shown that ozone depletion occurs over the latitudes that include North America, Europe, Asia, and much of Africa, Australia, and South America. Over the U.S., ozone levels have fallen 5-10%, depending on the season. Thus, ozone depletion is a global issue and not just a problem at the South Pole.

Reductions in ozone levels will lead to higher levels of UVB reaching the Earth's surface. The sun's output of UVB does not change; rather, less ozone means less protection, and hence more UVB reaches the Earth. Studies have shown that in the Antarctic, the amount of UVB measured at the surface can double during the annual ozone hole. Another study confirmed the relationship between reduced ozone and increased UVB levels in Canada during the past several years.

Laboratory and epidemiological studies demonstrate that UVB causes no melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to cataracts. All sunlight contains some UVB, even with normal ozone levels. It is always important to limit exposure to the sun. However, ozone depletion will increase the amount of UVB, which will then increase the risk of health effects. Furthermore, UVB harms some crops, plastics and other materials, and certain types of marine life.

The effect of ozone depletion on our health

Two chemicals singled out by the United Nations Environment Programme (UNEP) for their potential to damage the ozone layer may also cause human health problems.

Based on animal data, one of these chemicals, 1-bromopropane (1-BP), was recently reviewed by the National Toxicology Program Center for the Evaluation of Risks to Human Reproduction (CERHR) for its potential to harm human reproductive health, with the conclusion that more research is needed on its human health effects. Due to evidence of kidney tumors in animals, the other chemical, hexachlorobutadiene (HCB), has been classified by the U.S. Environmental Protection Agency (EPA) and the National Institute for Occupational Safety and Health as a possible human carcinogen.

UNEP issued a warning in September 2001 about 1-BP and HCB following reports of their increasing use as alternatives to hydrochlorofluorocarbons, which are banned and being phased out under the Montreal Protocol, an international agreement to discontinue use of ozone-depleting chemicals. 1-BP and HCB are not yet included in the Montreal Protocol, and because they break down close to the earth's surface,scientists believed they pose only a neglible threat to the ozone layer. But recent studies indicate that their long-term use under certain conditions actually may contribute to ozone layer damage.

A CERHR expert panel recently reviewed 1-BP for reproductive and developmental toxicity and is scheduled to release its final report in early spring 2002. A draft report points to the need for a well-designed human study with adequate exposure measurements. The NIEHS Environmental Toxicology Program, in conjunction with the National Institute for Occupational Safety and Health, is already funding some occupational exposure studies of 1-BP, says John Bucher, the program's deputy director.

In 2001, two manufacturers--Albemarle Corporation and Atofina--recommended that 1-BP not be used in applications in which worker exposure can't be tightly controlled, such as certain solvent or adhesive uses. Also, UNEP has asked parties to the Montreal Protocol to encourage industries to use 1-BP only when there is no alternative.

1-BP is known to be toxic in animals. Gaku Ichihara, a professor in the department of occupational and environmental health at Japan's Nagoya University, wrote in the May 2000 issue of Toxicological Sciences that after inhaling 1-BP, rats showed muscle weakness and deterioration of motor nerve function. Inhalation of 1-BP has also been shown to decrease fertility in male and female rats.

1-BP is used in spray adhesives and as a solvent in cleaning electronic components. People working with such applications can be exposed to 1-BP by inhalation or skin contact. There is currently no information indicating public exposure to 1-BP through air, food, or water, says CERHR director Michael Shelby.

According to Shelby, current usage of 1-BP is less than 5 million pounds per year. Although this may increase somewhat if 1-BP continues to be substituted for hydrochlorofluorocarbons, large increases in production don't seem likely because the chemical is very expensive compared to many other organic solvents and cleaners.

Although a December 2000 report from the California EPA titled Evidence on the Carcinogenicity of 1,3-Hexachlorobutadiene states that no data on long-term effects of human exposure to HCB have been found, there is evidence of toxicity in animals. Short-term skin contact with HCB has resulted in kidney, brain, and liver damage in rabbits, and rats and mice that ingested low concentrations of HCB over short and long periods developed kidney tumors and liver damage.

HCB is used as a solvent and to make lubricants and rubber compounds. The public could be exposed to HCB released into air, water, or soil during disposal of industrial waste, according to a toxicologic profile released by the Agency for Toxic Substances and Disease Registry. Some public drinking water contains HCB in amounts under the U.S. EPA maximum contaminant level of 1.0 ppb. The EPA Toxics Release Inventory for 2000 projected that 4,488 pounds of HCB would be released as waste that year in the United States.

Global warming

Higher temperatures threaten dangerous consequences: drought, disease, floods, lost ecosystems. And from sweltering heat to rising seas, global warming's effects have already begun. But solutions are in sight. We know where most heat-trapping gases come from: power plants and vehicles. And we know how to curb their emissions: modern technologies and stronger laws. NRDC is working to put these fixes in place. By shifting the perception of global warming from abstract threat to pressing reality, and promoting online activism. By pressing businesses to use less energy and build more efficient products. And by fighting for laws that will speed these advances. Together, these actions form a practical, economical approach to solving this urgent problem.

The effect of global warming

As the Earth continues to warm, there is a growing risk that the climate will change in ways that will seriously disrupt our lives. While on average the globe will get warmer and receive more precipitation, individual regions will experience different climatic changes and environmental impacts. Among the most severe consequences of global warming are:

• a faster rise in sea level,
• more heat waves and droughts, resulting in more and more conflicts for water resources;
• more extreme weather events, producing floods and property destruction; and
• a greater potential for heat-related illnesses and deaths as well as the wider spread of infectious diseases carried by insects and rodents into areas previously free from them.

If climatic trends continue unabated, global warming will threaten our health, our cities, our farms and forests, beaches and wetlands, and other natural habitats.

Who should be responsible for above problems?

Clearly, global warming is a huge problem. It will take everyone -- governments, industry, communities and individuals working together to make a real difference.

At UCS, we¡¦re working to bring sound scientific information to policymakers and the public to educate them about global warming, its impacts, and about available practical solutions. We¡¦re raising awareness of the need for action and working to create Congressional support for sound solutions.

But we don¡¦t stop there. We¡¦re also advocating policies that will combat global warming over the long term. Things like clean cars that run on alternative fuels, environmentally responsible renewable energy technologies, and stopping the clear-cutting of valuable forests.

These are solutions that will help to reduce global warming, and you can be part of them.

There are many little things everyone can do to help to reduce acid rain. If we all pitch in and do our part, we can vastly improve air quality, conserve water, and reduce the emission of fossil fuels. Here are ten things you can do to help:

1. Whenever possible, use public transportation, carpool, walk or ride a bike instead of driving your car by yourself.
2. Plan your errands efficiently to reduce the amount of driving you do.
3. Lower your home's heat at night and when you're away.
4. Install weather stripping to create a better seal on your home's windows and doors.
5. Run the dishwasher only if you have a full load of dishes.
6. Run the washing machine only if you have a full load of laundry.
7. Install water-efficient showerheads.
8. Reduce or avoid using air conditioning in your home and car.
9. Turn off lights when you leave a room.
10. Use energy efficient lightbulbs.

We can solute the problems brought by ozone depletion by accelerating phase-out of ozone depleting products, increasing public awareness for ozone protection and consumer incentives for non-ozone depleting alternatives are all timely for consideration.

On a national level, it is the role of federal government, states, and non-profit organizations to continue and expand efforts to explain and combat the problem of stratospheric ozone depletion to all generations, including its public health impacts and environmental risks. Most importantly, the public needs to become more actively engaged by making informed purchases and encouraging local governments and industry to eliminate production and use of all ozone-depleting substances.

The release of this report comes at a time when the issues surrounding the ozone layer depletion are receiving international attention. On September 16, 2003, the United Nations Environment Programme will host its annual "International Day for the Preservation of the Ozone Layer" to raise public awareness about ozone depletion and the steps that can be taken to help ensure the public¡¦s health and safety and the preservation of the Earth¡¦s critical ecosystems.