Toxicity

Outline: Page No:

1. INTRODUCTION 2

2. IDENTIFICATION OF AIR TOXIC PROBLEM 2

2.1 Sources of Air Toxics 2

2.2 Effects of Air Toxics on Human Health and Environment 4

3. REDUCTION AND REGULATIONS OF AIR TOXЭCS 5

4. CONCLUSION 7

REFERENCES 9

1. INTRODUCTION:

This chapter is about hazardous air pollutants which are also commonly konown as toxic air pollutants ora ir toxics and their toxicity effects. Air toxics can be defined as air contaminants that lead cancer or ather serious health effects , such as reproductive effects or birth defects, or adverse environmental effects. ( URL 1 ). In other words, if any compound that is in the air has the potential to produce adverse health effects, it can be technically entittled as air toxics( URL 2 ). The 1990 Clean Air Act Amendments 188 toxic air pollutants were reported by Environmental Protection Agency ( EPA ) that is required to control. Some examples of air toxics can be listed as benzene,perchloroethylyne, methylene chloride, toluene, cadmium, mercury, chromium, and lead compounds. ( URL 1 ).

It is important that to identify the source of toxic air pollutants, in order to determine the seriousness of the effects of toxics. The other significant point is to know effects of air toxics on environment and human health. After all, to minimize the side effects of toxic air pollutants , the ways for reduction of air toxics should be determined

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1. IDENTIFICATION OF AIR TOXЭC PROBLEM:

2.1 Sources of air toxics:

Millions of tons of air toxics are released into the air each year. Most of air toxics are mainly oriented from man-made sources. In addition to this some air toxics are released in major amounts from naturel sources such as forest fires

Figure 2.1 Sources Of Air Toxics ( URL 3 )

• Mobile Sources:

Mobile sources emissions can be described as emissions from motor vehicles. Such as, cars and light trucks, large trucks and buses, nonroad recreational vehicles ( e.g. dirtbikes and snowmobiles) , marine engines, aircrafts and locomotives.

• Stationary Sources:

Stationary sources are divided into two types:

 Major Sources:

They are defined as sources that emit 10 tons per year of single air toxics, or 25 tons per year of a mixture of air toxics. Examples of major sources are chemical plants, oil refineries, electric power plants, steel mills.

 Area Sources:

They release smaller amounts of air toxics into the air. Examples of area sources are neighborhood dry cleaners and gas stations. ( URL 3 )

Based on 1996 National Toxics Inventory data, major sources account for about 26 percent of air toxics emissions, smaller area sources and other sources (such as forest fires) for 24 percent, and mobile sources for 50 percent. Accidental releases, which also contribute air toxics to the atmosphere, are not included in these estimates.

Figure 2.2 Percentage Of Air Toxic Sources ( URL 3 )

2.2 Effects of air toxics on human health and environment:

Toxic air pollutants have great impact on human health and environment. Firstly, individuals are exposed to air toxics in many way, such as by;

 Breathing contaminated air

 Eating contaminated food

 Drinking water contaminated by air toxics

 Touching contaminated soil, dust or water

 Eating contaminated soil

Air toxics accumulate in body tissues after entering the body. Individuals and other animals at the top of the food chain are exposed to concentrations that are much higher than the concentrations in the water or soil.

Human exposure to these pollutants can include both short- term ( acute ) and long-term ( chronic ) complications. There are many factors that can affect the impaction of air toxics on human health which are listed below:

 Quantity which a person is exposed to

 The development stage of the person

 The duration and frequency of the exposure

 The toxicity level of the pollutant

 Person’s overall health and level of the resisitance ( URL 4 )

Short-term exposure effects can be defined as eye irritation, nausea and difficulty in breathing. On the other hand, long-term exposures have more dangerous effects on human health such as respiratory system damage, nervous system damage, birth defects, and reproductive effects.

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Figure 2.3 Diseases that Air Toxics Cause ( URL 5 )

In addition to this, toxic air pollutants have indirect effects on individuals through deposition onto soil or lakes, affecting ecological systems and finally human health through condumption of contaminated food (URL 5 ).

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