Ozone (O3) in Buildings • Sources • Fate • Effects • Measurement

Ozone (O

3

)

• Stratospheric good • Tropospheric bad (formation) • Standards / Regulations • Relative exposure analysis (include I/O) Exposure ( I / O )  C in t in B in C out t out B out     C in C out       t in t out       B in B out   

Exposure (I/O)

≈ (0.2 – 0.7) x 18 x 0.4 = 1.4 – 5

Health Effects

• Effects well understood (40+ years of research) • Inflammation of respiratory tissue • Irritation, coughing, pain upon deep breathing • Trische

et al

. (2006) – infants w/ mothers w/ asthma • Bell

et al.

(2006) – strong link to premature mortality

Sources of Ozone • Outdoor air

• typical source in urban area (summer) = 2 – 20 mg/hr

• Laser printers • Photocopy machines • Electrostatic precipitators • Explicit ozone generators

(100s – 1000s mg/hr)

• Ion generators

Ion Generators

• Enormously popular (M sold annually; > 1% homes) • Heavily marketed • Incidental O 3 formation • less than explicit O 3 generators • Claims often vague (arguably deceiving) • Comparatively ineffective • Often marketed with children in ad

Ozone

Indoor Reactions

Ozone Removal and By-Products

O 3 NO NO 2 VOCs NO 3

R R R R R R R R R BDB R P R

V dC dt



m inj

   

Q

 

j



v d,j A j

   

C

R R

Discussion of Practical area integrated deposition

stuff

Heterogeneous Reactions Homogeneous Reactions

Ozone + C=C

Ozone + specific VOCs (C=C) “bad stuff” Reactions in air AND on materials

Examples

– Styrene of C=C – d-Limonene – α/β-Pinene – Myrcene – α-Terpinene – Citronellol – Geraniol – Linalool alcohol – α-Terpineol Some Important Sources • Carpet (e.g., styrene) • Cleaning products • Polishes and waxes • Air fresheners • Other scented consumer products • Wood / plants

Potential Effects

• Odors • some aldehydes < 50 ppt; carboxylic acids to low ppb • Contact allergens (e.g., limonene oxidation products) Nilsson

et al

.,

Chromatographia

,

42

: 199-205 (1996) • Eye irritants (e.g., formaldehyde, acrolein) • terpene/ozone oxidation products Kleno and Wolkoff,

Intl’ Arch Occup. Environ. Health

,

77

: 235-243 (2004).

• Airway irritants • terpene/ozone oxidation products (HCHO, acrolein, …….) • 33% reduction in mean respiratory rate of mice (30 min) Wolkoff and Neilsen,

Atmospheric Environment

,

35

: 4407-4417 (2001); Wolkoff

et al

.,

Indoor Air

,

10

: 82-91 (2000); Clausen

et al

.,

Environment International

,

26

: 511-522 (2001) • Tox info not available for most oxidation products (!!)

Example: Solid Air Freshener

1,000,000.0

100,000.0

10,000.0

1,000.0

0.02-0.1

0.1-0.2

0.2-0.3

100.0

10.0

0.3-0.4

0.4-0.5

0.5-0.7

1.0

0.1

-50 50 150 250 350

TIM E [min]

450 550 650 750 Sarwar

et al

.,

Journal of the Air & Waste Management Association

,

54

: 367-377 (2004)

Chamber Experiment w/ Perfume

PM

1,000,000.0

O 3

+ 100,000.0

0.02-0.1

10,000.0

0.1-0.2

1,000.0

0.2-0.3

100.0

0.3-0.4

10.0

0.4-0.5

1.0

0.5-0.7

0.1

-50 0 50 100 150

TIM E [min]

200 250 300 350

Measurements

• Personal • diffusion-based (calculation in lecture) • Ambient • UV-absorbance http://www.ogawausa.com/passive.html

• 2B-Technologies • schematics (single and dual cell) • specifications http://www.twobtech.com/

Passive Ozone Samplers

http://www.ogawausa.com/passive.html

UV Absorbance

Summary

• Ozone inside of buildings is important – even if lower concentrations indoors – outdoor ozone breathed indoors to a great extent • Ozone + Reaction Products both health issues • Important to be able to predict indoor ozone levels • Important to be able to measure indoor ozone • Measurement technologies dramatically improved – cost, size (mobility)

VOCs in Buildings

• • • •

Sources Fate Effects Measurement

• What is a VOC?

– Organic = C, H – “affinity for gas phase”, “significant” evaporation rate – T b < 260 o C – Thousands (reduce list to 50 to 100) • What is TVOC?

Categories

• Odor-causing • Irritating • SBS – fatigue, eyes, headaches, upper resp., etc • Other – skin irritation, asthma, MCS • Toxic/Hazardous • Carcinogen • Teratogen • Neurotoxin, etc.

• Reactive • Generally w/ ozone

Representative Examples

• Benzene • Toluene • Ethylbenzene • Xylenes (all isomers)

BTEX

• Trimethylbenzenes (all isomers) • Dichlorobenzenes (not all isomers created equal) • Tetrachloroethene (PERC) • Chloroform (a THM) • 4-Phenylcyclohexene (4-PCH) • Styrene • Terpenes (limonene, pinene, etc.) • Formaldehyde (HCHO) – often not classified as a VOC

Relative Exposure to VOCs

Exposure ( I / O )  C in t in B in C out t out B out     C in C out       t in t out       B in B out   

Exposure (I/O)

= 3 x 18 x 0.4 = 22

indoor contribution > 95% (most volatile HAPs, etc.)

Some Important Sources

• Building materials and furnishing (wood, adhesives, gyp board) • Flooring materials (carpet, vinyl flooring, wood) • Architectural coatings (paints, varnishes, waxes, etc.) • Consumer products (cleaners, detergents, fresheners, personal, etc.) • Combustion sources (ETS, candles, gas stoves, space heaters) • Electronics (computers, photocopiers, printers, TVs/VCRs) • Heating of particulate matter • Soil vapor intrusion • Drinking water • Mold (MVOCs) • People

Measurement Issues

• Objective(s) • Required detection limits • (Real-time) vs. (collect and analyze) • Non-specific vs. species specific (speciated) • Grab versus integrated • Interferences • Preservation requirements • Quality assurance requirements • EPA/OSHA/NIOSH methods exist?

• Cost/Budget

Sample Collection Methods

• Real-time (field) measurement/analysis – generally = sensor (mostly FID, PID) – some = separation (w/ GC) + sensor – Also – colorimetric tubes (general: MDL > 1 ppm) • Collect for analysis – whole-volume samplers (canisters, bags) – concentration samplers (sorbents, SPME) – either case = preservation and analysis in laboratory

Canisters

• Whole volume • Grab versus integrated • EPA Methods TO-14 / 15 • Benefits • Inert/impermeable • Experience • Multiple analyses • Drawbacks • bulky • cleaning • Scratch • Ozone / Sample stability 1 – 15 L http://www.skcinc.com

400 mL

Tedlar Bags

• Whole volume • Tedlar = polyvinylfluoride • Pump to collect (unlike cans) • Issues: • Benefits: – inert / impervious (like cans) – repeat samples (like cans) – lighter than cans – lower initial cost than cans • Drawbacks – not as reuseable as cans – tearing – cleaning – stability with some compounds http://www.essvial.com/products/airsample.html

0.5 – 100 L

Sorbent Sampling

• VOC adsorbs to solid adsorbent • Passive sampling – Similar to ozone badge w/o reaction – Integrated sample over 24 hours, etc.

– Indoor, personal, outdoor • Active Sampling – Pump through packed tube – Collect mass over known volume – C = m/V – Short-term vs. integrated – More control, but more difficult http://www.aerotechpk.com/ http://www.sisweb.com/index/referenc/resin10.htm

Sorbent Tubes

• EPA Method TO-17 = TD/GC/MS (important) • Various sorbents can be used •TO-17 page 33 • Note VOC types/ranges • Some issues • Method detection limit, precision, accuracy (pg. 28/29) • Sample preservation • Breakthrough volume (see next slide) • Artifact formation (especially via ozone) • Sorbent pre-conditioning / breakdown over time • Use of multi-sorbent beds • Focus on Tenax-TA

Tenax-TA

• 2,6-diphenylene oxide polymer resin (porous) • Specific area = 35 m 2 /g • Pore size = 200 nm (average) • Density = 0.25 g/cm 3 • Various mesh sizes (e.g., 60/80) • Low affinity for water (good for high RH) • Non-polar VOCs (Tb > 100 o C); polar (T b > 150 o C) • lighter polar – Carbotrap and Carbopack-B common • Artifacts w/ O 3 : benzaldehyde, phenol, acetophenone

Solid-Phase Micro-Extraction

• • Short inside-out GC column • Coated fiber (extracting phase): – PDMS / DVB / Carboxen • Benefits – Highly concentrating for many indoor VOCs (ppt levels) – Reusable – Relatively low cost – Small / light weight – Possible use in other media – Ease of injection to GC • Drawbacks – Less experience / acceptability – Preservation issues – Difficulties w/ calibration – work-up

Gas Chromatography (GC)

• Goal = separate compounds • Use capillary column • Properties of column • Properties of chemical • Thermal program of GC oven • Temporal passage to a detector • analyze “peaks” • analyze molecular fragments (MS)

Gas Chromatography (GC)

http://www.chromatography-online.org/GC/Modern-GC/rs2.html

Figure 5: Chromatogram of Tenax-sampling in a show case (sample volume 1l) - iaq.dk/iap/iaq2003/posters/hahn5.gif

Blue slides = www.sisweb.com/art/referenc/aap54

GC Issues

• Type of injection?

• Need to cryofocus?

• Type of column?

• Type of detector?

– If MS, model of detection • Temperature programs • Instrument calibration / response

Detectors

• Flame ionization detector (FID) • Photoionization detector (PID) • Electron capture detector (ECD) Non-specific or speciated (w/ GC) • Mass spectrometer (MS) w/ speciated (w/ GC) • These are primary detectors for VOCs in indoor air • Specific uses vary considerably

Flame Ionization Detectors (FID)

• Relatively simple system  • Ions formed – migrate to plate • Generate current • Detection – typical to pg/s • Benefits – Rugged, low cost, workhorse – Linear response over wide range – Insensitive to H 2 O, CO 2 , SO 2 , CO, NO x • Drawbacks – No identification – Lower response if not simple HC – Destructive ..

www.chem.agilent.com

Photoionization Detectors (PID)

• UV light ionizes VOCs --- R + hv  • Drawbacks – No identification – Highly variable responses – Not all VOCs detected – Lamp burnout / contamination R + + e • Collected by electrodes = current • VOCs with different ionization potentials • Benefits – Simple to use – Sample non-destructive (relatively) http://www.chemistry.adelaide.edu.au/external/soc-rel/content/pid.htm

Electron Capture Detectors (ECD)

• Low energy Beta emitter = 63 Ni • e- attracted to positively charged electrode (anode) • Molecules in sample absorb e- and reduce current – effective: halogens (recall SF 6 ), nitrogen-containing • Benefits – 10-1,000 x more sensitive than FID – femtogram/s ----- ppt levels • Drawbacks – More limited linear range than FID – Radiological safety requirements – O 2 contamination issues http://www.chemistry.adelaide.edu.au/exte rnal/soc-rel/content/ecd.htm

– Response strong function of T, P, flowrate

Mass Spectrometer (MS)

• Bombard molecules w/ intense electron source • Generate positive ion fragments • Use fragment fingerprint to identify molecule • Quantify amount of fragments to determine mass • Most common MS = quadrupole

Quadrupole MS

• Electron source • Four rods (electromagnets) – Applied Voltage – DC/AC components – Voltages = fn(time) – Affects trajectory – Selective M/Z to detector • Cycles different M/Z • Yields mass spectrum • Always same for a molecule • System in vacuum http://www.chemistry.adelaide.edu.au/exter nal/soc-rel/content/quadrupo.htm

Total Ion Chromatogram (TIC)

linalool limonene Mondello

et al., J. of Chromatography A

, 1067: 235-243 (2005)

Mass Spectrum Example mass spectrum (fingerprint)

Mass Spectrometer

• Benefits – “Gold standard” – Amount AND identification of unknowns • Drawbacks – Cost – Complexity – Maintenance

Summary

• VOCs important in indoor environments • Many types of VOCs – Different properties – Different effects – Different sample collection and analysis protocols • Sampling and analysis protocols NOT TRIVIAL – Many types of collection methods – Many types of analysis methods / including detectors – A lot of issues involved w/ sample/analysis decisions – A lot can go wrong (difficult business) – Cumbersome and costly -------- but really important