environmental toxicology - iupac

Duffus & Worth, ©IUPAC 1

The Science of Chemical SafetyEssential Toxicology - 3

Environmental Toxicology

John Duffus & Howard WorthIUPAC Educators’ Resource Material

©IUPAC


Environmental Toxicology

• Large exposures to chemicals can affecthuman health directly or indirectly bydisrupting ecological systems that exist inrivers, lakes, oceans, streams, wetlands,forests and fields.

• The release of chemicals into theenvironment can have global impacts


Global Impacts - 1

• Chemicals can be transportedthroughout the atmosphere and are notbound by political borders

• DDT and its derivatives are found inthe Arctic and Antarctic.– They have never been used there


Global Impacts - 2

• Radionuclides from the Chernobylnuclear power station explosion in theUkraine in 1986 still contaminate farmsin Britain in 2000 and their lambscannot be sold for human consumption


Air Pollution - 1

• Acid precipitation (acidic rain, snow,particulates etc) is a result of air pollutioncaused by burning fossil fuels such as coaland oil and other compounds containingnitrogen and sulfur

• Acid precipitation results from the solution ofnitrogen and sulfur oxides to give a mixtureof nitrous, nitric, sulfurous and sulfuric acids


Air Pollution - 2

• Acid precipitation may reduce the pHof lakes below 6, releasing aluminiumions which kill the fish– Note - above pH 6, aluminium in water is

increasingly in the form of hydroxideswhich are not bio-available


Air Pollution - 3

• The products of burning fossil fuels arenitrogen oxides (NOx), sulfur oxides(SOx), volatile organic compounds(VOC), carbon oxides (carbon monoxideand carbon dioxide), and particulates

• Environmental damage may result from carbonmonoxide (CO) and carbon dioxide (CO2)contributing to the “greenhouse effect”


Air Pollution - 4

• The “greenhouse effect” is heating ofthe environment because heat loss fromthe surface of the earth through theatmosphere is reduced by reflection ofinfrared radiation from gases andvapours such as CO2 and water vapour

• See slide 17 on global warming


Air Pollution - 5• Air pollution affects human health

directly as a result of lung damage andindirectly through damage to crops,buildings, and acidification of naturalwaters– Sulfur and nitrogen oxides aggravate

bronchitis and asthma, putting stress on theheart: they killed more than 4,000 people,mostly elderly, in London in 1952 as adirect result of these harmful health effects


Air Pollution - 6

• Volatile organic compounds (VOCs), insunlight, react with ozone to producehighly reactive compounds which attacklung tissue

• Carbon monoxide reduces oxygenuptake by binding to haemoglobin

• Inhaled particulates reduce lung function


Preventing Air Pollution• Methods available for reducing emissions of

acid rain include burning low sulfur fossilfuels, trapping pollutants in emitting stacks(for example - trapping the sulfur oxides withlime, CaO, to make gypsum, CaSO4), andremoving sulfur from coal and other fuels– Note - trapping pollutants may still leave a

problem of waste disposal although, in theexample given, gypsum can be used to makecement


Preventing Air Pollution - 2

• Each preventive method has itsbenefits, and all have their associatedcosts– Trapping the sulfur oxides has been

favoured in some countries but it posesthe problem of what to do with excessgypsum if there is already enough tomeet demand for cement


The formation and distribution of acid precipitation- acid rain, acid fog and acid particulates

Long distance rain

Local rain

Acid fogs

Ozone

Acid rain

Acid rain

Sunlight

Dry particulate fallout

NOx, SOx, VOC, CO, CO2


Stratosphere Ozone Depletion

• Ozone depletion in the upperstratosphere is a worldwide problemthat has required co-operation by worldleaders

• Ozone in the stratosphere protects usfrom the harmful effects of excessultraviolet radiation from the sunwhich, among other things (see below),causes skin cancer


The Montreal Protocol• CFCs - chlorofluorocarbons (formerly

used extensively as refrigerants andsolvents) have entered the stratosphereand catalytically reacted with the ozonethere, reducing the amount so much thatholes have appeared in the ozone layer

• The Montreal Protocol of 1987 is aninternational treaty signed by manycountries agreeing to reduce the releaseof CFCs


Effects of Ozone Depletion

STRATOSPHERICOZONE

DEPLETION

Photochemicalformation oftropospheric

ozone

CLIMATECHANGE

Accumulationof acid aerosols

Crop &forestdamage

Humanrespiratory

illness

Suppressionof immunity

Directhuman

health effects

More infectiousdisease: less

effective vaccinationMore skin

cancer

Morecataracts and

blindness

Damage to materialssuch as paint, plastic

& rubber

Reducedcrop yields;stunted plant

growth

Reductionin plankton

and fishpopulations

INCREASED UVRADIATION AT THEEARTH’S SURFACE


Global Warming - 1

• It appears that the earth is slowly rising intemperature (global warming)– Global warming is thought to be due to

increasing levels of carbon dioxide and watervapour in the atmosphere caused by large scaleburning of fossil fuels

– The carbon dioxide and water vapour permitradiation from the sun to heat the earth butprevent loss of heat, in the form of infraredradiation (the greenhouse effect)


Global Warming - 2

• Increased earth temperature is changingthe climate and thus the ecology allround the world– Increased temperature increases the rate of

transformation of chemicals by micro-organisms and facilitates transfer ofvolatile substances through the air


Environmental Exposure Routes• All the changes that occur in the

environment affect people

• Ultimately people can be exposed toany substance that enters theenvironment

• Some of the more obvious routes ofexposure of people are shown in slide21


Risk Assessment forEnvironmental Exposure

• Risk assessment for the possible effectsof any substance entering theenvironment which may harm peoplemust sum up the exposures through allroutes in order to determine the totalexposure and then the possible effect


Air

Soil

Surfacewater

Groundwater

CropsCattle Milk

Fish

Drinking water

PEOPLE

Potential exposure routes in assessing exposure to the general public


Self Assessment - 3.1True or False?

• Some chemicals can spread throughout theworld from their point of release - see slide 3

• Acid rain contains nitric and sulfuric acids -see slide 5

• Acidification of natural waters to pH 6.5 isenough to poison fish - see slide 6

• Air pollution affects only human beings - seeslides 6 & 18


Self Assessment - 3.2True or False

• Trapping sulfur oxides as gypsum is thesolution to the problem of air pollution - seeslide 11

• Environmental effects of chemicals may causeharm indirectly by increasing exposure tonatural components of the environment - seeslides 14 to 18

• The same chemical can reach humans bydifferent routes; the total exposure by all routesdetermines the harm caused - see slides 20 and21


Self Assessment - 3.1Checklist

• Some chemicals spread throughout thewhole world from their point of release -True

• Acid rain contains nitric and sulfuric acids- True

• Acidification of natural waters to pH 6.5is enough to poison fish - False

• Air pollution affects only people - False


Self Assessment - 3.2Checklist

• Trapping sulfur oxides as gypsum willsolve the problem of air pollution - False

• Environmental effects of chemicals maycause harm indirectly by increasingexposure to natural components of theenvironment - True

• The same chemical can reach humans bydifferent routes; the total exposure by allroutes determines the harm caused - True

environmental toxicology - iupac

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