Acid Rain Q & A

Posted: 01-Jan-2000; Updated: 28-Dec-2006

What Is Acid Rain?

Acid rain is precipitation -- rain, snow, sleet, and fog -- combined with chemical emissions that cause harm to our waters, forests and human health.

What Causes Acid Rain?

Acid rain is caused by the emission of harmful chemicals such as sulfur dioxides, the leading cause of acid rain, and nitrogen oxides. These chemicals result from the burning of coal to produce electricity, non-ferrous metal smelting and, to a lesser extent, fuel combustion in vehicles. Once these pollutants are released into the atmosphere, they can be converted into secondary chemical pollutants such as nitric acid and sulfuric acid. Both of these pollutants are easily dissolved in water and result in acidic water in the form of rain, snow, sleet and fog.

Are Acid Deposits Always Wet?

No. Acidic pollutants also exist as drops of dry acid and as gases. In this gaseous state they can be deposited dry. Dry deposits produce the same damage as wet deposits.

How Does Acid Rain Affect Aquatic Ecosystems?

As rivers, lakes and streams become more acidic they lose their ability to sustain fish and other aquatic life. In extreme cases, whole lakes or steams can become lifeless, except for algae. Acid rain also has a significant affect on the food chain. For example, terrestrial animals depend on aquatic organisms for nourishment and nutrients and are affected as food sources decline or are eliminated.

How Does Acid Rain Affect Plant Life?

There are multiple pollutant stresses on vegetation and crops. For example, acid rain increases soil weathering and nutrient removal. Also, it reduces the rate of tree growth and weakens the condition of some trees like red spruce. In such a weakened state, trees are more susceptible to disease, drought and severe climatic conditions.

How Does Acid Rain Affect Animal Life?

Habitats and food resources can be affected resulting in population decline due to stress (because of decrease in food resources) and lower reproductive rates. For example, some animals depend on aquatic organisms for nourishment and nutrients. As food resources are reduced or eliminated, the quality of the animal's habitat declines and the reproductive successes of the animal are affected.

How Does Acid Rain Affect Human Health?

Acid rain causes the food, water, and air we breathe to be contaminated with acidic pollutants. For example, acid rain can increase the levels of toxic metals such as aluminum, copper and mercury in untreated drinking water supplies. Also, studies conducted in Canada and the U.S. indicate that there is a link between acidic particulates and respiratory problems. It is estimated that death rates in the most polluted areas are 15% higher than those in the least polluted areas, due in part to such particulates.

What Is Environmental Defense Doing to Combat Acid Rain?

The goal of Environmental Defense is to cut the emissions that cause acid rain in half by using an emissions trading system. Under our plan, the Environmental Protection Agency (EPA) issues utilities a selected number of "allowances" to emit pollutants. For example, if the pollution level in a particular region is one million tons per year, the EPA issues each utility in that region a selected number of "allowances" that total one million tons.

How Does Emissions Trading Work?

If a particular utility emits 5 tons of pollution annually, the EPA can tell them to reduce that to 4 tons the next year. Utilities must keep their emissions within their established allowances. Utilities can earn more allowances by emitting less or buying allowances from another utility. If the utility emits less than the allocated amount, it can save its leftover credits for future use or sell them.

What Can You Do?

Reduce the amount of energy you use in your home. Turn off lights and electrical appliances when not in use. Purchase energy saving appliances. Purchase clean-running cars and maintain them so that they continue to run clean. Decrease the amount of driving you do. Drive less aggressively. Use public transportation whenever possible. Contact your Congressional representatives and ask them to strengthen the Clean Air Act. Also, ask them to regulate automobile manufacturers to ensure the production of cleaner running cars. Another way you can combat acid rain is by purchasing an emission credit. That's one less credit to which utilities have access. Please contact the EPA for more information on how to buy a credit.