Indoor Air Quality: Aerosol Particles and Pollutants

Aerosol Particles in Indoor Air

Indoor air quality is affected by various aerosol particles, including:

• Heavy metals
• Man-made mineral fibres (MMMF)
• Natural fibres (asbestos)
• Tobacco smoke
• Combustion products from stoves, fireplaces, and chimneys

Definition of Aerosols

An aerosol is a suspension of solid and liquid particles of different shapes and chemical compositions in the air.

Heavy Metals and Bioaccumulation

Common heavy metals include mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), thallium (Tl), and lead (Pb).

• Heavy metals are natural components of the Earth's crust.
• They cannot be degraded or destroyed.
• They enter human bodies via food, drinking water, and air.
• Heavy metals tend to bioaccumulate (their concentration in a biological organism increases over time compared to the concentration in the environment).

Cadmium and Chromium Applications

Cadmium: The most significant use of cadmium is in nickel-cadmium batteries or as cadmium coatings (galvanized).

Chromium: Hexavalent chromium is used for the production of stainless steel, textile dyes, wood preservation, leather tanning, and as anti-corrosion paints and coatings (such as primer paint in aerospace and automobile refinishing applications).

• Chromium compounds are often found in soil and groundwater at abandoned industrial sites, which now require environmental cleanup.

Heavy Metal Extraction via Earthworms

In the extraction of heavy metals using earthworms, the earthworms excrete a slightly different version of the metals, making them easier for plants to suck up.

Man-Made Mineral Fibres (MMMF)

MMMF can cause cancer and tumors. Carcinogenicity is more closely related to the physical size of fibres than to differences in mineralogical composition.

Types and Uses of Mineral Wools

• Mineral fibres and mineral wools are made from molten blast-furnace slag or other fusible slags, natural rocks, and minerals (such as basalt and diabase).
• They provide excellent heat and sound insulation.
• They are used as materials for fire protection, including spray fireproofing in stud cavities in drywall assemblies and as packing in firestops.

Asbestos Regulation and Safety

Worldwide, 60 countries (including those in the European Union) have banned the use of asbestos. Safety standards often monitor levels such as 1,000 fibres/m³.

Protocols for Asbestos Removal

An enclosure for asbestos removal work must include:

• An airlock for personnel entering and leaving the enclosure.
• Exhaust ventilation creating an underpressure of at least 5 Pa within the enclosure.
• An air change rate in the enclosure of at least 8 per hour.
• A direct connection to the decontamination unit.

Air Cleaning Technologies

Electronic Cleaners and Ionizers

Electronic air cleaners (electrostatic precipitators) draw air through an ionization section where particles obtain an electrical charge. Charged particles then accumulate on a series of flat plates called a collector that is oppositely charged. Note: Electronic air cleaners can produce ozone, a lung irritant.

Ionizers disperse charged ions into the air. These ions attach to airborne particles, giving them a charge so that they attach to nearby surfaces (such as walls or furniture) or attach to one another and settle faster. Note: Ionizers can also produce ozone.

Mechanical Air Filtration

Mechanical air filters remove particles by capturing them on specialized filter materials.