Mould Growth on Building Materials VOC Analysis by Solid Phase Micro-extraction (SPME)

Transcription

1 Mould Growth on Building Materials VOC Analysis by Solid Phase Micro-extraction (SPME) Karen Bartlett, PhD, Raymond Li, MSc and Tom Barnjak, BSc School of Occupational & Environmental Hygiene University of British Columbia

2 Introduction Outline Introduction to Mould Introduction to Preservatives The Study Methods Materials & Experimental conditions Sample Preparation Sampling Technique Analytical Methods Results Conclusions

3 What are Moulds? Moulds are filamentous fungi

4 Why is this Important? Mould Components are associated with various health effects. spores and hyphal fragments hypersensitivity/allergy reactions conidia (spore) Metabolites Mycotoxins Highly toxic and can cause a variety of health problems including death. Volatile Organic Compounds (VOCs) responsible for odors may be the cause of irritation symptoms, sick building syndrome conidiophore hyphae

5 Where are they found? Moulds are found everywhere in the environment. Mostly we are not concerned Unless, they are found in our homes.

6 How to Prevent Mould Growth? Moulds can grow on most building materials All that is needed is a source of food (cellulose), moisture and right temperature (most are happy at room temperature). How to control their growth? Control moisture Use naturally resistant materials Use preservatives What is the easiest thing to do?

7 Controlling moisture.not that easy

8 How to Prevent Mould Growth? Using naturally resistant materials Not easily available, shrinking forests, hardwood is becoming scarcer everyday. Must use preservatives, but there is a problem Most common preservative is Chromated Copper Arsenate (CCA) Contains Arsenic which is a known carcinogen CCA in not recommended for residential use, not in use since 2003 What are the alternatives? Borate compounds Low toxicity, can be used to treat various materials

9 Borates Disodium octaborate tetrahydrate (DOT) water-soluble, used in solid lumber Zinc borate (ZnB) relatively insoluble, used in wood composites Boric acid used in cellulose insulation for fire resistance also used in gypsum board to improve material and processing properties

10 Aim of the Study Investigate the effectiveness of borate- based preservatives at preventing mould growth on building materials Are borates effective? At what concentrations?

11 Materials Treated and untreated materials were supplied and were tested with five different species of moulds Southern yellow pine Lodgepole pine Pine oriented strandboard (OSB) Aspen OSB Solid wood Wood composites Cellulose fiber insulation Gypsum board 6 different levels of boric acid (0 to 5 lbs per 1000 sq. ft.) were tested

12 Experimental Design Each gypsum board experiment consisted of two specimens at each boric acid level one inoculated on the front face and one on the back face plus a control (uninoculated piece). All experiments were done in triplicate Organism A.fumigatus C.cladosporides S.chartarum A.Versicolor P.brevicompactum 0 lbs boric acid/msf 1 lb/msf 2 lbs/msf 2.57 lbs/msf 4 lbs/msf 5 lbs/msf F B F B F B F B F B F B

13 Sample Preparation Sterilized by irradiation Conditioned for 2 weeks at 100% RH Inoculated with 100 µl of mould spore suspension with an airbrush Incubated for 4 weeks at room temperature ( C) and ~100% RH in sealed chambers

14 Monitoring Growth was monitored by Weekly visual inspection Scores assigned based on percentage surface area covered and intensity: 0 = no growth 1 = hyphae only 2 = spores just visible 3 = more obvious sporulation 4 = heavy sporulation/discolouration

15 Monitoring Cont. Weekly changes in VOC profile by SPME on GC/FID Level of CO 2 at the end of experiment Level of Ergosterol by GC/MS

16 Sampling VOC sampling was done with Solid Phase Micro- extraction (SPME). Adsorption time was 30 minutes.

17 Solid Phase Micro-extraction (SPME) Major Features Retractable sampler - contains a tip of fused silica coated with a film of adsorbing materials Plunger needle allows use with GC or GC/MS, HPLC 75 µm Carboxen/Polydimethylsiloxane (PDMS) coating Suitable for gases and low molecular weight compounds (MW )

18 Why use SPME for sampling? Experimental chamber atmosphere must remain undisturbed for 4 weeks Need a way to sample the atmosphere without disturbing it SPME is a perfect solution Does not disturb/alter atmosphere in the chamber Very sensitive Self cleaning and reusable Adsorptive coating can be chosen for compounds of interest Some problems with SPME Very fragile Exposure times and temperatures need to be carefully controlled Low boilers/high boilers maybe problematic

19 Analytical Methods VOC analysis done with a Varian 3400 GC/FID SPME desorption time: 4 minutes Instrument Parameters Column Type: RTX-VMS 0.25 mm I.D. x 30 meters (1 µm df) Temperature Program: Initial Temperature 40 o C (4 min hold) Ramp 1: to 140 o 8 o C/min Ramp 2: to 200 o 5 o C/min (3.5min hold) Injection Port Temperature: 230 o C Splittless Injection Time: 0.50 min Detector Temperature: 220 o C

20 Mould VOC Profiles Different species of mould produce different VOC profiles Marker compounds need to be carefully chosen Mould growth is assessed by looking for catabolism (consumption) of naturally occurring VOCs and anabolism (production) of new mould specific VOCs Controls in the experiments consist of an uninoculated (sterile) piece of gypsum board.

21 Results Gypsum Board inoculated with A. fumigatus at week 4 Control 5lb/1000 ft 2 4lb/1000 ft lb/1000 ft 2

22 Results Cont. Gypsum Board inoculated with A. fumigatus at week 4 Control 2lb/1000 ft 2 1lb/1000 ft 2 0lb/1000 ft 2

23 Results - VOCs from all Species Rt 2.4 min Furan Acetone 2-butanone Dimethyl furan 2-pentanone Dimethyl disulfide Dimethyl cyclopentenone Methyl pyrrole Rt 10.9 Rt 11.3 Rt 12.9 Pyrrole 2-hexanone Styrene 1-hexanol 2-heptanone Anisole Limonene Methoxy-2-methyl benzene 2-octanone Ethoxy methyl benzene 2-nonanone Rt 21 Rt 23 Rt 24 Rt 25 C9 cyclic ketone Rt 27 Trichodiene Compound southern yellow pine lodgepole pine pine OSB aspen OSB cellulose insulation gypsum board Other terpenes

24 Results: effects of borate preservatives Carbon dioxide (gypsum board) Error bars are 2 SEM Av erage carbon diox ide - S. chartarum / gy psum board Av erage carbon diox ide - A. versicolor / gy psum board carbon dioxide (ppm) carbon dioxide (ppm) boric acid (lbs/msf) 0 lbs 1 lbs 2 lbs 2.57 lbs 4 lbs 5 lbs boric acid (lbs/msf) 0 lbs 1 lbs 2 lbs 2.57 lbs 4 lbs 5 lbs Av erage carbon diox ide - P. brevicompactum / gy psum board 6000 carbon dioxide (ppm) boric acid (lbs/msf) 0 lbs 1 lbs 2 lbs 2.57 lbs 4 lbs 5 lbs

25 Results: effects of borate preservatives Ergosterol (gypsum boards) Error bars are 2 SEM Av erage ergosterol - S. chartarum / gy psum board Av erage ergosterol - A. versicolor / gy psum board 3 3 ergosterol (ug/ cm2) ergosterol (ug/cm2) <DL <DL <DL <DL <DL <DL boric acid (lb/msf) 0 lbs 1 lbs 2 lbs 2.57 lbs 4 lbs 5 lbs boric acid (lb/msf) 0 lbs 1 lbs 2 lbs 2.57 lbs 4 lbs 5 lbs Av erage ergosterol - P. brevicompactum / gy psum board 3 ergosterol (ug/cm2) <DL <DL <DL boric acid (lb/msf) 0 lbs 1 lbs 2 lbs 2.57 lbs 4 lbs 5 lbs

26 Conclusions Borate-treated treated materials do resist mould growth Borates inhibit mould growth in a dose-dependent dependent manner Borates suppress the formation of VOC metabolites Incorporating borates into building materials may provide a measure of protection against mould growth This method of monitoring mould VOCs can be used as a bench top screening tool for potential preservative compounds

27 Acknowledgments School of Occupational & Environmental Hygiene (SOEH) Karen Bartlett, PhD Raymond Li, MSc Winnie Chu, PhD Funding: U.S. Borax, Genics and Michael Smith Foundation Website: We welcome collaboration with others