Unit 7

Unit 7

Part I

Introduction

I. Read the text, explain the main problems of the theme

Principles of Toxicology

Sixty thousand chemical substances are sold commercially in the United States. By various estimates, 8600 food additives, 3400 cosmetic ingredients, and at least 35000 pesticides are in use. Chemical production and use have skyrocketed since World War II. Of the commercially important chemicals, however, only a small number – per haps 2% - are known to be harmful. Still, this small percentage amounts to hundreds of potentially dangerous chemicals, hazardous mainly to workers but also to the general public, as the Bhopal tragedy makes clear. According to the Department of Transportation, more than 62000 accidents during the transportation of toxic wastes occurred in the United States between 1980 and 1987. The human cost in comparison with Bhopal was small – 2756 people killed and injured. Many more accidents occur in the workplace and in toxic waste facilities.

Per haps the biggest problem with toxic substances is our lack of knowledge about their effects. The National Academy of Sciences notes that fewer than 10% of US agricultural chemicals and 5% of food additives have been fully tested to assess chronic health effects. Testing potentially harmful substances is a costly and time-consuming task, made more difficult by the 700 to 1000 new chemicals entering the market place each year.

II. Study the vocabulary

1. estimate, n - оценка

2. skyrocket, v – устремляться ввысь, быстро расти

3. hazardous - рискованный, опасный

4. facilities,pl- средства

5. lack - недостаток

6. assess,v - расценивать

III. Give the annotation of the text

Part II

I. Read the text

Biological Effects of Toxins

Toxic substances, or toxins, are chemicals that adversely affect living organisms. Toxicology is the study of these effects. Our concern is primarily with the effects on humans.

Average citizens are exposed to toxic substances at home, at work, or while moving about outdoors. In many cases they have little control over exposure. Polluted air from nearby power plants or highways exposes them to dozens of potentially harmful substances. In some cases, however, we intentionally expose ourselves to harmful substances, such as smoke from cigarettes.

Chemical substances exert a wide range of effects, depending on the amount we receive. This amount, in turn, is determined by the concentration (or dose) of the toxin and the duration of the exposure – known as the two D’s (dose and duration). Some effects may be subtle, such as a slight cough or headache caused by air pollution. Others can be pronounced, such as the violent convulsions brought on by exposure to certain insecticides. Toxicologists, the scientists who study toxins, classify effects as acute and chronic.

Acute effects are those symptoms that appear right after exposure. Acute effects often disappear shortly after the exposure ends and are generally caused by fairly high concentrations of chemicals during short-term (acute) exposures.

Chronic effects are delayed, but long-lasting, responses to toxic agents. They may occur months to years after emphysema caused by cigarette smoke or pollution. Chronic effects are generally the result of low level exposure over long periods.

Chemicals can affect virtually every cell in the body. Their hidden effects, such as cancer, mutations, birth defects, and reproductive impairment, pose the most serious challenge to society.

Cancer annually kills 500000 people in the United States. Cancer is an uncontrolled proliferation of cells that forms a mass, or primary tumor. Cells may break off from the tumor and travel in the blood and other body fluids. The spread of cancerous cells is called metastasis. In distant sites the cancerous cells may from secondary tumors.

Mutations - agents that cause mutations are called mutagens. In general three types of genetic alteration are seen: (1) changes in the DNA itself, (2) alterations of the chromosomal structure that are visible by microscope, and (3) missing or extra chromosomes.

Birth Defects. Seven percent of children born have a birth defect: a physical (structural), biochemical, or functional abnormality.

II. Study the vocabulary

1. adversely - неблагоприятно, вредно

2. exposure – подвергание риску, опасности, распространение

3. expose,v- подвергать

4. exert,v – оказывать влияние

5. be subtle – быть незначительным, слегка уловимым

6. a slight cough – слабый кашель

7. violent convulsions – неистовые, очень сильные судороги

8. insecticides – порошок против насекомых

9. acute effect – сильное воздействие

10. сhronic effect – хроническое действие

11. emphysema - эмфизема

12. cancer – рак

13. reproductive impairment – врожденное отклонение организма

14. proliferation – размножение

15. primary tumor – первичная опухоль; опухоль в начальной стадии.

Unit 8

I. Read the text

Economy and Ecology

Man’s economic activity has nowadays become commensurate with the effect of the planetary forces. But the economic might be attained through human effort has intrinsic contradictions.

In the history of industrial production raw materials have tended to be used to extract one or two components: one type of ore would be used to extract iron, another type – to extract copper, and so forth. Whatever is left after extraction would be dumped as waste.

Tens of billions of tons of raw materials are processed by the world’s industries every year, and the amount doubles every 15 years. Today, 98 per cent of the extracted resources are discarded as “waste”.

Formerly, when extraction rates were relatively show and industrial output small, the impacts of economic activity were not so clearly felt. That led to a totally wrong theory that nature was capable of self – decontamination. No such “self – decontamination“ has ever occured!

Human intervention in natural processes develops on a growing scale. The heaviest impact has been on the world ocean and inland water bodies, such as lakes and rivers. Because of extensive and still increasing extraction of oil from offshore oilfields, the world ocean is getting heavily polluted.

Air pollution presents a global problem. The smokes discharged by factories are carried by winds hundreds and thousands of kilometres away from industrial areas. Upon contacting atmospheric moisture, compounds of sulphur and nitrogen turn into acid. Acid rain produces a lethal effect upon open – air plants and small animals, fishes and water – weeds. The world’s forests, which maintain the air and water balance on the planet, and provide for the fertility of soils and preservation of the flora and fauna, have also been jeopardized. All these factors taken together affect human health.

In recent years, when the destructive impact of man’s economic activity upon the world’s ecosystems became so glaringly evident, the dilemma – economy or ecology – has been debated with growing vigour. Which way to go – to keep boosting economic growth, or to liberate resources for nature conservancy programmes?

II. Study the Vocabulary

1. commensurate – соответственный, соразмерный

2. attain,v – достигнуть, добиться

3. intrinsic – существенный

4. extract,v – извлекать, вырабатывать

5. self – decontamination – самообеззараживание (очищение)

6. moisture – влажность, сырость

7. compounds of sulphur and nitrogen – соединение серы и азота

8. acid – кислота

9. fertility – плодородие

10. preservation – сохранение

11. jeopardize,v – подвергать опасности, рисковать

12. boosting economic growth – повышенный экономический рост

13. liberate,v – выделять

14. conservancy – охрана лесов и озер