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How Ozone Pollution Works

Introduction to How Ozone Pollution Works

The weather report on the radio or TV tells you that it is going to be sunny and hot and that an orange ozone alert has been issued. What is ozone? What does an orange alert mean? Why should you be concerned about it?

In this article, we will examine what ozone is, how it is produced, what health hazards it poses and what you can do to reduce ozone pollution.

Ozone is a molecule of three oxygen atoms bound together (O3 ). It is unstable and highly reactive. Ozone is used as a bleach, a deodorizing agent, and a sterilization agent for air and drinking water. At low concentrations, it is toxic.

Ozone is found naturally in small concentrations in the stratosphere, a layer of Earth's upper atmosphere. In this upper atmosphere, ozone is made when ultraviolet light from the sun splits an oxygen molecule (O2 ), forming two single oxygen atoms. If a freed atom collides with an oxogen molecule, it becomes ozone. Stratospheric ozone has been called “good” ozone because it protects the Earth's surface from dangerous ultraviolet light.

Ozone can also be found in the troposphere, the lowest layer of the atmosphere. Tropospheric ozone (often termed “bad” ozone) is man-made, a result of air pollution from internal combustion engines and power plants. Automobile exhaust and industrial emissions release a family of nitrogen oxide gases (NOx) and volatile organic compounds (VOC), by-products of burning gasoline and coal. NOx and VOC combine chemically with oxygen to form ozone during sunny, high-temperature conditions of late spring, summer and early fall. High levels of ozone are usually formed in the heat of the afternoon and early evening, dissipating during the cooler nights.

Although ozone pollution is formed mainly in urban and suburban areas, it ends up in rural areas as well, carried by prevailing winds or resulting from cars and trucks that travel into rural areas. Significant levels of ozone pollution can be detected in rural areas as far as 250 miles (150 km) downwind from urban industrial zones.

Make Your Own Ozone Detector

You can make ozone test strips to detect and monitor ozone levels in your own backyard or around your school. You will need:

corn starch

filter paper (coffee filters work well)

potassium iodide (can be ordered from a science education supplier such as Carolina Biological Supply or Fisher Scientific)

Basically, you make a paste from water, corn starch and potassium-iodide, and you paint this paste on strips of filter paper. You then expose the strips to the air for eight hours. Ozone in the air will react with the potassium iodide to change the color of the strip. You will also need to know the relative humidity, which you can get from a newspaper, weather broadcast or home weather station.

Avoiding and Reducing Ozone

When you inhale ozone, it travels throughout your respiratory tract. Because ozone is very corrosive, it damages the bronchioles and alveoli in your lungs, air sacs that are important for gas exchange. Repeated exposure to ozone can inflame lung tissues and cause respiratory infections.

Ozone exposure can aggravate existing respiratory conditions such as asthma, reduce your lung function and capacity for exercise and cause chest pains and coughing. Young children, adults who are active outdoors and people with respiratory diseases are most susceptible to the high levels of ozone encountered during the summer.

In addition to effects on humans, the corrosive nature of ozone can damage plants and trees. High levels of ozone can destroy agricultural crops and forest vegetation.

Avoiding Ozone Exposure

To protect yourself from ozone exposure, you should be aware of the Air Quality Index (AQI) in your area everyday—you can usually find it in the newspaper or on a morning weather forecast on TV or radio. You should also be familiar with the U.S. Environmental Protection Agency (EPA) guide for ozone-alert values.

What do the numbers in the AQI mean? The AQI measures concentrations of five air pollutants: ozone, sulfur dioxide, particulate matter, carbon monoxide and nitrogen dioxide. The EPA has chosen these pollutants as criteria pollutants, but these are not all of the pollutants in the air. These concentrations are compared to a standard set out in federal law. An index value of 100 means that all of the criteria pollutants are at the maximum level that is considered safe for the majority of the population.

To reduce your exposure to ozone, you should avoid exercising during afternoon and early evening hours in the summer.

Reducing Ozone Pollution

There are several ways you can help to decrease ozone pollution:

Limit using your automobile during afternoon and early evening hours in the late spring, summer and early fall.

Do not use gasoline-powered lawn equipment during these times.

Do not fuel your car during these times.

Do not light fires or outdoor grills during these times.

Keep the engine of your car or boat tuned.

Make sure that your tires are properly inflated.

Use environmentally safe paints, cleaning and office products (some of these chemicals are sources of VOC).

Conserve energy.

Besides personal attempts to reduce ozone pollution, the EPA has initiated more stringent air-quality standards (such as the Clean Air Act and its modifications) to reduce air pollution. Compliance with these standards by industries, manufacturers and state and local governments has significantly reduced the levels of many common air pollutants.

With continued conservation and reduction practices, adherence to ozone- pollution warnings, research and government regulation, ozone-pollution levels should continue to fall. Perhaps future generations will not be threatened by this environmental pollutant.

How can ozone be both good and bad?

The thing that determines whether ozone is good or bad is its location.

Ozone is “good” when it is in the stratosphere. The stratosphere is a layer of the atmosphere starting at the level of about 6 miles (about 10 kilometers) above sea level. The stratosphere naturally contains about six parts per million of ozone, and this ozone is very beneficial because it absorbs UV radiation and prevents it from reaching us.

Ozone is “bad” when it is at ground level. Ozone is a very reactive gas that is hard on lung tissue. It also damages plants and buildings. Any ozone at ground level is a problem. Unfortunately, chemicals in car exhaust and chemicals produced by some industries react with light to produce lots of ozone at ground level. In cities, the ozone level can rise to a point where it becomes hazardous to our health. That's when you hear about an ozone warning on the news.

1. Ozone can not be used as _____.

A. a bleach

B. a oxidizer

C. a deodorizing agent

D. a sterilization agent for air and drinking water

2. High levels of ozone are usually dissipating _____.

A. in the heat of the afternoon and early evening

B. during sunny, high-temperature conditions of late spring, summer and early fall

C. during the cooler nights

D. during the summer

3. What is not needed to make ozone test strips?

A. Corn starch.

B. Coffee.

C. Filter paper.

D. Potassium iodide.

4. Which part of your body is affected most from ozone?

A. Cardiovascular system.

B. Blood cholesterol.

C. Digestive tract.

D. Respiratory tract.

5. To protect yourself from ozone exposure, you should be aware of _____.

A. the newspaper in your area everyday

B. a morning weather forecast on TV or radio in your area everyday

C. the Air Quality Index in your area everyday

D. the U.S. Environmental Protection Agency guide for ozone-alert values

6. To reduce your exposure to ozone, you should avoid exercising _____.

A. during afternoon and early evening hours in the summer

B. during afternoon in the late spring, summer and early fall

C. during early evening hours in summer and early fall

D. during afternoon in the late spring and early fall

7. What is not mentioned as a way that helps to decrease ozone pollution?

A. Do not light fires or outdoor grills during afternoon and early evening hours in the late spring, summer and early fall.

B. Ride bicycles, dim the lights, and take fewer showers.

C. Do not fuel your car during afternoon and early evening hours in the late spring, summer and early fall.

D. Make sure that your tires are properly inflated.

8. With continued conservation and reduction practices, adherence to ozone-pollution warnings, research and government regulation, ozone-pollution levels should continue to _____.

9. When ozone is in the stratosphere, it is very beneficial because it absorbs UV radiation and _____.

10. Chemicals in car exhaust and chemicals produced by some industries react with light to produce _____.

文章精要：

文章主要介绍什么是臭氧。包括臭氧污染的形成、危害，以及臭氧有利的一面。文章还具体介绍了如何自己手工制作检测仪；然后避免暴露在臭氧底下；如何预防和减少臭氧污染以及臭氧有利的一方面。

答案解析：

1. B　根据题干中的信息词Ozone can not be used as定位到第一个小标题下的第三段第三句。原文提到臭氧可以用作a bleach漂白剂（选项A），a deodorizing agent除臭剂（选项C），a sterilization agent杀菌药（选项D），但未提到可以被用作氧化剂（a oxidizer），故选B。

2. C　根据题干中的信息词High levels of ozone和dissipating定位到第一个小标题下的第五段末句。题目问的是大量臭氧在什么时候消散，原文提到大量的臭氧通常在温度较高的午后和傍晚形成，在较冷的夜间消散，故选C。

3. B　根据题干中的信息词needed to make ozone test strips定位到第二个小标题下的第一段第二句可知：为了进行臭氧试验，你需要corn starch玉米淀粉（选项A），filter paper过滤纸（选项C），potassium iodide碘化钾（选项D），未提到需要咖啡，故选B。

4. D　根据题干中的信息词your body is affected most from ozone定位到第三个小标题下的首句。题干问的是身体的哪一部分受臭氧的影响最大，原文提到：当你吸入臭氧时，它会经过整个呼吸道，由此可以推断臭氧影响的主要是人体的呼吸道（respiratory tract），故选D。

5. C　根据题干中的信息词To protect yourself from ozone exposure定位到第四个小标题下的首句。题干问的是为了使你自己不暴露在臭氧下，应该注意什么，原文提到：为避免暴露在臭氧下，人们应该注意每天所在区域的空气质量指数，故选C。

6. A　根据题干中的信息词To reduce your exposure to ozone定位到第四个小标题下的末句。题干问的是为了减少在臭氧中的暴露，你应当避免在什么时间锻炼；原文提到：为了减少在臭氧中的暴露，应当避免在夏天的午后和傍晚锻炼，故选A。

7. B　根据题干信息词a way that helps to decrease ozone pollution定位到第五个小标题下的首段。原文提到：减少臭氧污染有几种方法，选项中的A、C、D都在其中提到，只有选项B“骑自行车、减暗灯的亮度和少洗淋浴”没有提到，故选B。

8. fall。根据题干中的信息词continued conservation和reduction practices定位到第五个小标题下的末段首句。题干的表述与原文相同，故答案为fall。

9. prevents it from reaching us。根据题干中的信息词absorbs UV radiation定位到第六个小标题下的第二段末句。题干问的是当臭氧在同温层时，它是很有益的，因为它能吸收紫外线辐射并且_____；原文提到这种臭氧（在同温层中的臭氧）非常有益，因为它能吸收紫外线辐射并防止其照射到我们，故答案为prevents it from reaching us。

10. lots of ozone at ground level。根据题干中的信息词Chemicals in car exhaust定位到第六个小标题下的倒数第一段第五句。原文提到：汽车尾气及工业废气中的化学物质与光反应会在地表产生许多臭氧，故答案为lots of ozone at ground level。