1.5 Human pollution

Monday, May 1, 2023Scott Lucas

Dwight School London, 2015

Assessment statementsSignificant ideas• SI1.5.1 Pollution is a highly diverse phenomenon of

human disturbance in ecosystems.• SI1.5.2 Pollution management strategies can be

applied at different levels.

Assessment statementsKnowledge and understanding• U1.5.1 Pollution is the addition of a substance or an agent to an

environment through human activity, at a rate greater than that at which it can be rendered harmless by the environment, and which has an appreciable effect on the organisms in the environment. Pollutants may be in the form of organic or inorganic substances, light, sound or thermal energy, biological agents or invasive species, and may derive from a wide range of human activities including the combustion of fossil fuels. [The terms “pollutant” and “contaminant” in environmental chemistry are considered more or less synonymous.]

• U1.5.2 Pollution may be non-point or point source, persistent or biodegradable, acute or chronic. [Pollution which arises from numerous widely dispersed origins is described as non-point source. Point source pollution arises from a single clearly identifiable site.] [“Biodegradable” means capable of being broken down by natural biological processes]

Knowledge and understanding• U1.5.3 Pollutants may be primary (active on emission) or

secondary (arising from primary pollutants undergoing physical or chemical change). [Students should be aware that for some pollutants there may be a time lag before an appreciable effect on organisms is evident.]• U1.5.4 Dichlorodiphenyltrichloroethane (DDT)

exemplifies a conflict between the utility of a “pollutant” and its effect on the environment. [Students might demonstrate knowledge of both the anti-malarial and agricultural use of DDT.]

Assessment statementsApplications and skills• S1.5.1 Construct systems diagrams to show the impact of

pollutants.• S1.5.2 Evaluate the effectiveness of each of the three

different levels of intervention, with reference to figure 3.• S1.5.3 Evaluate the uses of DDTInternational-mindedness• Pollution cannot be contained by national boundaries and

therefore can act either locally, regionally or globally.

Vocabulary• Acute: a large amount of pollution released rapidly• Biodegradable: capable of being broken down by natural biological

processes• Chronic: a small amount of pollution released long-term• Lag time: the period of time between when a pollutant is released

and when the effect of the pollutant is detected• Non-point source pollution: pollution which arises from numerous

widely dispersed origins• Persistent organic pollutants (POPs): resistant to breaking down and

remain active in the environment for a long time• Point source pollution: pollution from a single clearly identifiable site• Pollution: the addition of a substance or agent to an environment by

human activity, at a greater rate than that at which it can be rendered harmless by the environment , and which has an appreciable effect on the organisms within it

SI1.5.1 Pollution is a highly diverse phenomenon of human disturbance in ecosystems.• Pollutants can be• Matter: gas, liquid or solid which is organic or inorganic• Energy: sound, light, heat• Living organisms: invasive species or biological agents

U1.5.1 Pollution is the addition of a substance or an agent to an environment through human activity, at a rate greater than that at which it can be rendered harmless by the environment, and which has an appreciable effect on the organisms in the environment. Pollutants may be in the form of organic or inorganic substances, light, sound or thermal energy, biological agents or invasive species, and may derive from a wide range of human activities including the combustion of fossil fuels. [The terms “pollutant” and “contaminant” in environmental chemistry are considered more or less synonymous.]

U1.5.2 Pollution may be non-point or point source, persistent or biodegradable, acute or chronic.• Pollutants may be classified as

• Point source: released from a single, clearly identifiable site ex. factory chimney or waste disposal pipe or sewage works into a river• Easier to identify the polluter• (Usually) easier to manage as it can found more easily• Solution: fine polluters and install system to reduce pollution

• Non-point source: released from numerous, widely dispersed origins ex. exhaust from vehicles, chemicals spread on fields• Many sources means it is impossible to identify where it is coming from• Rainwater can transport nitrates/phosphates increasing the

concentration in lakes/rivers far from the sources• Air pollution can be blown hundreds of km and chemicals from

chimneys may mix with others• Solution: set limits for all and monitor what they emit (expensive to

monitor)

U1.5.2 Pollution may be non-point or point source, persistent or biodegradable, acute or chronic.• Pollutants may be classified as• Persistent organic pollutants (POPs): resistant to

breaking down and remain active in the environment for a long time• Can therefore bioaccumulate in animal tissues and biomagnify

up food chains/webs• Ex. DDT, PVC (polyvinyl chloride), PCB (polychlorinated

biphenyls), etc• High molecular weight• Not very soluble in water• Highly soluble in fats (pass through cell membranes)• Halogenated molecules (typically chlorine)

• PCBs were banned in 2001 because they cause cancer, disrupt hormone function• Found in water and animal tissues as far as the Artic Circle

U1.5.2 Pollution may be non-point or point source, persistent or biodegradable, acute or chronic.• Biodegradable: capable of being broken down by natural

biological processes• Break down quickly by decomposers or physical processes such

as light or heat• Ex. soap, domestic sewage, degradable plastic bags (starch),

glyphosate herbicide (by soil organisms)

U1.5.2 Pollution may be non-point or point source, persistent or biodegradable, acute or chronic.• Pollutants may be classified as• Acute: a large amount of pollution released rapidly

• Ex. Bhopal Disaster 1984• Chronic: a small amount of pollution released long-term

• Serious problem because• Often goes undetected for a long time• Usually more difficult to clean up• Often spreads widely

• Ex. air pollution like in Beijing: causing non-specific respiratory diseases such as asthma, bronchitis, emphysema

U1.5.3 Pollutants may be primary (active on emission) or secondary (arising from primary pollutants undergoing physical or chemical change). [Students should be aware that for some pollutants there may be a time lag before an appreciable effect on organisms is evident.]• Two types• Primary pollutants: active on emission ex. carbon

monoxide results in headache and fatigue, death• Secondary pollutants: are formed when primary

pollutants change physically or chemically ex. sulphur trioxide + water sulphuric acid• NB: photochemical smog is a mixture of both (6.3)

• Lag time: the period of time between when a pollutant is released and when the effect of the pollutant is detected

Measuring pollution• Can be measured indirectly or directly• Direct, air pollution

• Acidity of rainwater• Amount of gas in the atmosphere (CO2, CO, NOx)• Amount of particples emitted by a diesel engine• Amount of lead in the atmosphere

• Direct, water/soil pollution• Nitrates and phosphates• Amount of organic matter or bacteria• Heavy metal concentrations

Measuring pollution• Indirect: record changes in abiotic or biotic factors that

are the result of pollutants (therefore indirect measure of pollution• Abiotic factors: dissolved oxygen in water• Biotic factors: indicator species, either present or absent

• Ex. Lichens on trees = unpolluted• Ex. Rat-tailed maggots in water = polluted

SI1.5.2 Pollution management strategies can be applied at different levels.• Pollution can be managed at three levels

1. By changing human activities to prevent/reduce the release of pollutants

2. By preventing or regulating the production/release of pollutants

3. By working to clean up or restore damaged ecosystems

• The principles of this sub-topic, particularly figure 3, should be usedthroughout the course when addressing issues of pollution

• With reference to figure 3, you should be able to appreciate the advantages ofemploying the earlier strategies of pollution management over the later ones,and the importance of collaboration

S1.5.2 Evaluate the effectiveness of each of the three different levels of intervention, with reference to figure 3.

Activity

Release

Restoration

S1.5.1 Construct systems diagrams to show the impact of pollutants.• Task: construct a systems diagram to show

pollution of a local ecosystem (PSOW)

U1.5.4 Dichlorodiphenyltrichloroethane (DDT) exemplifies a conflict between the utility of a “pollutant” and its effect on the environment. [Students might demonstrate knowledge of both the anti-malarial and agricultural use of DDT.]• DDT was banned in 1970 by WHO• Still used in small amounts in some tropical countries for

spraying inside houses to kill malarial mosquitos• Did banning DDT do more harm than good?• Estimated malaria: kills 2.7 million a year – mostly children

under five, infects 300-500 million a year• It is thought that DDT prevented millions of deaths• Rachel Carson in Silent Spring argued that DDT thinned bird

eggs reducing populations • Some argue the evidence for thinning is slight and DDT is

effective against malarial moquitos

U1.5.4 Dichlorodiphenyltrichloroethane (DDT) exemplifies a conflict between the utility of a “pollutant” and its effect on the environment. [Students might demonstrate knowledge of both the anti-malarial and agricultural use of DDT.]• DDT is still sprayed on walls and backs of furniture to kill/repel

adult malarial mosquitos• DDT is effective, cheap and persistent though other chemicals

could be used• The persistence and toxicity is what lead to the ban in the first

place and eventually resistance will develop• Malaria is increasing due to resistance, changing land use,

migration of people to malarial areas• DDT is one tool to combat malaria including other chemicals,

mosquito nets and removing stagnant water• Malaria is a disease of the poor and so probably doesn’t get as

much funding as it should

S1.5.3 Evaluate the uses of DDT• Task: Create a poster/website/wiki on the benefits

and disadvantages of using DDT.• What evidence can you find for both sides of the

argument?• Be careful in looking at sources. Are they biased? Can

they substantiate their claims?• Do you now think that DDT should have been banned or

should it still be used?

Visit ProjectEd for more resources

https://sites.google.com/a/dwightlondon.org/projected/

Works Cited• International Baccalaureate Organization. Diploma

Programme Environmental systems and societies guide. The Hague: IB Publishing Ltd, Feb. 2015. PDF.• Rutherford, Jill. Environmental Systems and

Societies. Oxford: OUP, 2015. Print.