AP Environmental Science Unit 7 Notes: Indoor Air Pollution (Sources, Impacts, and Solutions)

Indoor air pollution

The presence of harmful chemical, physical, or biological substances in the air inside buildings (e.g., homes, schools, offices).

Exposure

How much contact a person has with a pollutant; often high indoors because people spend a lot of time inside and sources may be close to where they breathe.

Dose (environmental health)

The amount of pollutant that enters the body; depends on concentration, time of exposure, and route of entry (indoors, mainly inhalation).

Bathtub analogy (indoor air)

A way to model indoor pollution: sources are the “faucet,” ventilation is the “drain,” and pollutant concentration builds when emissions exceed removal.

Ventilation

Exchange of indoor air with outdoor air; dilutes/removes many pollutants but can also bring in outdoor pollutants (e.g., pollen, wildfire smoke).

Source control

Reducing indoor pollution by removing the source or preventing release (often the best long-term strategy).

Filtration (indoor air)

Air cleaning method that is most effective for particles (PM, dust, pollen, some mold spores) but generally not for gases like CO or radon.

Carbon monoxide (CO)

A colorless, odorless gas produced by incomplete combustion (e.g., faulty furnaces, gas stoves, generators indoors, car exhaust in attached garages); causes acute poisoning by reducing oxygen delivery in the body.

Incomplete combustion

Burning that does not fully oxidize fuel to CO2 and water, producing pollutants such as carbon monoxide (CO).

CO poisoning mechanism

Inhaled CO binds strongly to hemoglobin, reducing oxygen transport to tissues and causing symptoms like headache, dizziness, and nausea.

Nitrogen oxides (NOx)

Gases produced by high-temperature combustion (including gas stoves) that can irritate airways and worsen asthma; also linked to outdoor ozone/smog chemistry.

Particulate matter (PM)

Tiny solid and liquid particles suspended in air (e.g., from wood smoke, candles, cooking, tobacco); fine particles can penetrate deep into lungs and affect respiratory/cardiovascular health.

Environmental tobacco smoke (secondhand smoke)

A complex indoor pollutant mixture containing particulate matter (PM), VOCs, and other toxic substances; increases risk of respiratory illness, especially in children.

Volatile organic compounds (VOCs)

Carbon-based chemicals that evaporate easily at room temperature (off-gas) from products like paints, cleaners, adhesives, and new carpets; can irritate eyes/nose/throat and trigger headaches/asthma symptoms.

Off-gassing

Release of chemicals (often VOCs) from new materials or products into indoor air, especially after renovations or installation.

Formaldehyde

A commonly discussed indoor VOC that can be emitted from certain pressed-wood products and some furnishings.

Integrated Pest Management (IPM)

A strategy to reduce pesticide exposure by emphasizing prevention and targeted control (seal entry points, reduce food/water, use traps/baits, and apply chemicals only as needed).

Radon

A radioactive, odorless gas from the natural decay of uranium in soil/rock that can seep into buildings and increase long-term lung cancer risk (higher risk for smokers).

Sub-slab depressurization

A radon mitigation method using a vent pipe system and fan to draw radon from beneath a foundation and exhaust it above the roofline.

Sick building syndrome

A pattern where occupants report symptoms (e.g., headaches, irritation, fatigue) linked to time spent in a building, often due to ventilation problems and mixed low-level pollutants.

Asbestos

Naturally occurring mineral fibers once used for insulation/fireproofing; most dangerous when disturbed, releasing inhalable fibers that can cause lung scarring and cancers after long latency periods.

Abatement/encapsulation (asbestos)

Professional methods to safely remove or seal asbestos-containing materials to prevent fiber release; preferred over DIY disturbance or vacuuming.

Lead (indoor exposure)

A toxic metal often encountered indoors via deteriorating lead-based paint and lead-contaminated dust; harms the nervous system, with children especially vulnerable due to hand-to-mouth exposure.

HEPA filter

A high-efficiency particle filter designed to capture very small particles; helpful for PM, dust, pollen, and some spores, but not effective for gases like CO or radon.

Mold (indoor pollutant)

A fungus that releases spores; becomes an indoor air pollutant when moisture allows growth and spores/fragments become airborne, triggering allergies and worsening asthma—best controlled by fixing the moisture source.