VOCs in Indoor Air

Armin Wisthaler

Norsk institutt for luftforskning

Norsk Innemiljøorganisasjon, 17.04.2012

Indoor air and health

A series of health symptoms and health effects have been associated with poor indoor air quality:

• respiratory and ocular mucosa irritation

• nausea, dizziness

• headache, fatigue

• increased sensitivity to odors

• asthma and allergic airway disease

• cancer

Volatile organic compounds (VOCs)

• Exposure to indoor VOCs has been suggested as one of the potential causes for the observed health symptoms/effects in the indoor environment.

• VOCs are gaseous, carbon-containing chemical compounds.

• Hundreds/Thousands of VOCs have been found in indoor air at ppt-to-ppm (10-12 -10-6 v/v) levels.

• Indoor air contains a broader variety and higher levels of VOCs than outdoor air.

• Exposure to indoor VOCs includes peak exposures to selected VOC (e.g. solvents from fresh paint) and low-level chronic exposure to complex mixtures of VOCs.

Sources of indoor VOCs

• building materials: paints, flooring and wall materials, HVAC materials, adhesives/varnishes

• furnishing: furniture, fabrics, electronic equipment (TV sets, monitors, PCs, printers, ...)

• consumer products: cleaning agents, air freshener, perfumes/cosmetics

• human activities: cooking, heating (open fireplace)

• living organisms: humans, pets, plants, bacteria, mold/fungi

taken from: Organic Indoor Air Pollutants, 2009

VOCs from paints

taken from: Indoor Air Quality Handbook, 2001

but: unspecified

VOCs from paints

taken from: Indoor Air Quality Handbook, 2001

VOC emissions over time

• early emissions (hours) peak exposure

• mid-term emissions (days)

• late emissions (weeks)

• long-term emissions (months) chronic long-term exposure

Wolkoff, 1998

VOCs from floor and wall covers

• carpets

• flooring (PVC, linoleum, rubber, polyolefin, wood)

• wall covers and panels (polystyrene, plywood, etc.)

• adhesives, waxes, varnishes

VOCs from carpets, parquet wood

taken from: Indoor Air Quality Handbook, 2001

VOCs from vinyl flooring

Yu and Crump, 1998

C13 (tridecane) TXIB (2.2.4-trimethyl-1.3-pentanediol diisobutyrate)

steady-state

VOCs from floor varnish

Wolkoff, 1998

odor threshold: 47 g/m3

VOCs from human activities

cooking, heating, cleaning,….. taken from: Organic Indoor Air Pollutants, 2009

Indoor concentrations of VOCs

fundamental parameters: emission rate / ventilation rate

figure courtesy: C. Weschler

Ventilation and indoor air quality • To increase buildings energy efficiency, ventilation rates

tend to decrease (improved air tightness, natural or hybrid ventilation).

• Reduced ventilation rates cause indoor VOC levels to increase.

• The use of low/zero-VOC materials/products becomes essential.

figure courtesy: C. Weschler

Traditional VOC emission research

- temperature - relative humidity - air exchange rate - air velocity - loading factor (surface-to-volume ratio)

material product

VOC

taken from: Organic Indoor Air Pollutants, 2009

Examples of emission test chambers

Indoor VOCs and reactive chemistry

• Indoor air has has traditionally been viewed as an unreactive matrix (VOC source: materials/products; VOC sink: ventilation)

material product

VOCprimary

R VOCsecondary

material product

R

VOC*

* only emitted in the presence of R

Indoor VOCs and reactive chemistry

O3

OH

NO2

NO3

HNO2

N2O5

Products of indoor chemistry • Reactive indoor VOC chemistry forms oxidized, nitrated,

nitrosated compounds, including mono- and multi-functional species.

• Products of indoor chemistry are anticipated to be more harmful than primary VOCs.

• Products of indoor chemistry are difficult to measure with traditional analytical techniques.

Nucleation condensation

O3 + primary

emission

Products of indoor chemistry

• Indoor ozone chemistry forms particles.

figure courtesy: C. Weschler

Ozone + >C=C<

Products of indoor chemistry

styrene / terpenes /terpenoids

target products reference

carpet aldehydes Weschler et al., 1992 Morrison and Nazaroff, 2002 Wang and Morrison, 2006

Latex paint low VOC paint (lineseed oil)

formaldehyde, aldehydes aldehydes, organic acids

Reiss et al., 1995a,b Wang and Mossiron, 2006 Andersson et al., 1996

HVAC materials (neoprene gasket, duct liner, duct sealants)

aldehydes Morrison et al., 1998

“green” building materials (clay paint, miner fiber tile, fabric wall panel, recycled carpet, hardwood floor, resilient tile, clay tile)

aldehydes Lamble et al., 2011

wood and wood products, polymeric materials,....

• odors

• contact allergens

limonene oxidation products (e.g. Nilsson et al.,1996)

• eye irritants terpene/ozone oxidation products (e.g. Kleno and Wolkoff, 2004)

• airway irritants terpene/ozone oxidation products (e.g. Wolkoff et al., 2000, Wolkoff and Niesen, 2001)

Products of indoor chemistry

Summary

• A multitude of indoor VOC sources causes peak VOC exposures (e.g. fresh paint) and chronic long-term exposures to mixtures of VOCs.

• The use of low/zero-VOC materials/products is recommended.

• Reducing the ventilation rate increases indoor VOC concentrations.

• The introduction of highly reactive compounds into

the indoor environment should be avoided.