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Identify sources of human health issues that are linked to pollution.

Establishing Cause and Effect

three interconnected circles, each depicting a different issue: obesity, asthma, and pollution, three overlapping forces impacting health, highlighting the complex interplay of these factors. — **Human health is complex. It is sometimes difficult to figure out how pollutants affect human health.**

Although we have learned a lot about the connections between pollution and human health, it is still difficult to establish a cause and effect between the two because humans are exposed to so many different chemicals and pollutants.

The number of variables to which we’re exposed creates difficulties in pinpointing exactly which pollutant caused exactly what effect in a human. All humans are not exactly alike, either, or some may react to pollutants that have little, if any, effect on others.

For example, air pollution can have damaging effects on the human respiratory system, but so can obesity and a lack of vitamin D.

If a patient reports to a doctor with asthmatic symptoms, it’s almost impossible to determine which of these actually caused the damage to the respiratory system - or if they all contributed to the symptoms. On top of that, some people have preexisting medical issues that may or may not increase or decrease the impacts of the pollution on their health.

The bottom line is that we know that pollutants impact human health. We are still trying to figure out all the potential connections between all the different pollutants and human health.

Essential Knowledge

It can be difficult to establish a cause and effect between pollutants and human health issues because humans experience exposure to a variety of chemicals and pollutants.

Exposure!

Acute exposure occurs when a large dose of a pollutant is absorbed in a short period of time. An example of acute exposure is the inhalation of a toxic gas. Chronic exposure occurs when a small amount of a pollutant is absorbed repeatedly over a long period of time. An example of chronic exposure is an alcoholic who drinks for many years and suffers liver damage from that chronic exposure to alcohol.

There are three ways routes of exposure to pollutants:

three distinct ways substances can enter the human body: inhalation, absorption, and ingestion. — ***Pollutants can be inhaled through the nose, absorbed through the skin, or ingested through the mouth.***

Chemicals can interact together to have effects that are greater or smaller than what you’d expect. This is why doctors often ask for any medications you are currently taking before prescribing you additional medications.

Three different types of interactions: additive (2+2=4), synergistic (2+2=10), and antagonistic (2+2=0). — ***Additive effects are what you'd expect. Synergistic effects are greater than expected and antagonistic effects cancel each other out.***

Accidental overdoses of medication are often synergistic effects.

Pollutants Affecting Human Health

While it’s difficult to put a label on each pollutant due to their different interactions, we can categorize pollutants in general groups based on the biological effects that they have been shown to cause in humans. In general, pollutants fall into the following categories:

- 😷 Carcinogens: cancer-causing (ex: asbestos, tobacco smoke)
- 🧬 Mutagens: cause changes in DNA (ex: x-ray, UV rays)
- 👩🏻‍🍼 Teratogens: cause birth defects (ex: mercury, alcohol)
- 💐 Allergens: cause allergic reactions (ex: pollen, dust, pet dander)
- 🧠 Neurotoxins: cause neurological damage (ex: lead, mercury)
- 🤰 Endocrine disruptors: cause reproductive issues (ex: BPA, DDT, PCB)
- 🦠 Pathogens: cause infectious disease (ex: dysentery)
- 💨 Environmental Reactants: substances that interact with the environment (ex: tropospheric ozone)

For example, asbestos is a carcinogen, which means that exposure to asbestos can cause cancer, specifically mesothelioma. Each pollutant can be classified accordingly, based on what type of effect it has on humans. Some pollutants can have multiple classifications. Mercury is a carcinoge, a teratogen and an endocrine disruptor.

Essential Knowledge

Dysentery is caused by untreated sewage in streams and rivers.

Mesothelioma is a type of cancer caused mainly by exposure to asbestos.

Respiratory problems and overall lung function can be impacted by elevated levels of tropospheric ozone.

AP Exam Tip

You should know how pollutants affect human health.

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