Consequences of Large-scale Production of Marijuana in Residential Buildings

Abstract

Based on the data from the breadth of Canada (∼4300 km), one-third of Canadian homes have ventilation rates below the recommended standard of 0.3 air changes per hour and are at risk for moisture problems. For the purposes of this investigation, a literature review was performed on the health risks associated with exposure to living and drying marijuana plants and the fungi associated with large numbers of indoor plantings. Analysis was made of the impact on Canadian homes if used to grow marijuana. These are commonly called “marijuana grow operations” based on measured ventilation rates from homes in Windsor, Ontario and Regina, Saskatchewan (representing diverse climates) and derived moisture loadings from published data. The growing and drying of marijuana plants contributes considerable amounts of water vapour to the indoor environment. Depending on the scale of production, considerable mould damage in the building can result. There are also a number of abiotic hazards resulting from marijuana production including pesticides, carbon monoxide, and products of unvented combustion appliances. Both indirect and direct evidence are described for the health impact of living in these conditions. This has a number of implications in terms of documentation and personal protection for industrial hygienists, home inspectors, and public health officials.

Keywords

Health Marijuana grow operations Ventilation rates Moisture

Introduction

Canada is second to the USA among industrialized nations in marijuana production, although it is illegal to produce and sell this plant in both nations. This demand has caused an increase in the number of illegal “marijuana grow operations” (MGOs) in homes [1,2]. To 2003, the average number of seized plants in Ontario MGOs was ca. 340. The exposed population to these conditions is not well defined. As a proxy for the total, ca. 1000 children were found in a 3-year period in MGOs in Ontario and the estimated total number might be considerably larger, 10,000 [3]. A study from the greater Vancouver area indicated many MGOs are “guarded” by immigrant families including young children (ca. 20%), and that these families are accessing the health care system [4]. Across Canada, there is an increasing number of former MGOs that were not detected by the police. These homes are often purchased by unsuspecting people who face both health and legal challenges, although the exact number of affected people is not known [5,6].

In 2001, the Canadian Medical Marijuana Access Regulation (MMAR) [7] came into effect. In terms of population size, there were 4900 license holders of whom 3600 grow between 2 and 292 marijuana plants for personal use in January 2010 (http://www.hc-sc.gc.ca/dhp-mps/marihuana/stat/index-eng.php). This option is not available in the USA. The percentage of licensees that grow their own plants has been stable at ∼70% for some years; the remaining individuals pool their permits to a maximum of three. The average number of plants grown by individuals is 25. Approximately, 2000 physicians issue permits under these regulations. The larger, legal MGOs in Canada potentially pose many of the same risks as illegal MGOs.

There are two main sources of moisture associated with the cultivation of marijuana indoors (1) moisture from the cultivation of the plant and (2) moisture arising from the drying of the plant. These sources are additional to those associated with the normal operation of the house or apartment building. These may include occupant sources, water leaks and ventilation failure leading to condensation [8 –11]. Increased moisture results in growth of the saprophytic fungi characteristic of damp building materials [12,13]. Such growth is a function of internal moisture source strength [9]. Cultivation and drying of marijuana in residential dwellings may result in extensive environmental contamination and damage to the building. A study of illegal MGOs across Canada found that 11 of 12 had serious mould and moisture damage and evidence of the use of large amounts of pesticides and fertilizers. An attempt is made to keep grow operations warm and humid, and the odour of growing marijuana is distinctive, i.e. detected by authorities and/or neighbours. For both these reasons, efforts are made to seal the buildings to avoid detection [6]. This reduces the designed ventilation rate for the homes and hence moisture removal.

The purpose of this paper is to describe the potential damage and public health consequences of the input of additional moisture to the air within residential housing from the growth and drying of different numbers of large plants indoors in the existing housing stock in representative cities in Canada. We calculated the moisture load that a typical marijuana plant adds to a house. This is interpreted in relation to how this relates to mould growth on the building fabric and the effects of saprophytic mould on population health. Except under controlled conditions, the dominant fungus on drying plants is Aspergillus fumigatus, an allergenic species and a facultative pathogen. Additional literature reviews were conducted in order to evaluate the health risks more specific to the conditions associated with marijuana production in residential environments.

Methods

Moisture release of potted plants varies from 7 to 15 g·h⁻¹ [14]. Based on the moisture release rate of a related plant [15] and scaled for mass after Kaa [16], a full-grown marijuana plant was calculated to release 18 g·h⁻¹ of water vapour (432 g·day⁻¹). This value is consistent with an estimate by Christian [17].

Typically, moulds require a water activity (a_w) of at least 0.80–0.85 to promote rapid growth [13,14]. Like all “medicinal” plants, marijuana is at a much increased risk of mould growth during the drying period after harvest unless appropriate equipment is used. During this time, water previously bound to cells becomes available to fungi as the plant begins to decay. Dead and drying plant material with moisture contents above ∼12% has an a_w sufficient to promote fungal growth. Moisture content >20% in drying plant material promotes rapid fungal growth [18]. This formed the indirect evidence to exposure from moulds on the plants, which were more directly answered by looking at concentrations of moulds on the marijuana and from patient reactions to smoking it.

Measured ventilation rates in winter were obtained from CMHC and Health Canada for 59 homes in Windsor and 103 in Regina (Wheeler, Heroux, Fugler, unpublished data). This was done by the Oak Ridge National Laboratory method; also, see Ref. [19] for an explanation of the method. Conditions in Windsor, Ontario (hot and humid in summer, moderate in winter) and Regina, Saskatchewan (moderate in summer; cold and dry in winter) were calculated and measured data were obtained for Ottawa (hot, often cold in winter) [20,21]. These cities represent communities with different climates in Canada. Growth of fungi on drying plants was assessed from the literature and from objective data.

Information on health effects of dampness and housing was taken from recent cognizant authority reviews [22 –27]. A literature search of published peer reviewed journal articles was conducted in early 2009 for additional hazards that might relate to marijuana production in houses. The following databases were included: Web of Science, PubMed, EMBASE, MEDLINE, the Cochrane Library, Sci Finder, government documents and those of professional groups. The search included publications from 1978. Boolean searching was used to combine up to 20 keywords and/or MESH headings. Keywords were classified as fungal (e.g. fungi, mould, A. fumigatus), environmental hazard (e.g. pesticides, herbicides, defoliant), relating to marijuana grow operations (e.g. marijuana, cannabis, MGOs), health (e.g. rhinitis, dermatitis, lung function), and moisture. Studies were assessed for relevance and whether they met all the Klimisch criteria [28]. The primary screening process involved one reviewer screening ca. 5000 articles. Two reviewers conducted the secondary screening process applying the relevance and quality criteria independently for the 300 studies selected. Biological and chemical contaminants arising from medium to large-scale cultivation of marijuana were identified during this process.

Results

Moisture Burdens

As plants are added to an MGO, moisture release will overwhelm home ventilation capacity and/or worsen the situation, if ventilation failure already exists. In Canada, the recommended combined infiltration and mechanical ventilation is 0.3 air changes per hour (ac·h⁻¹) for a household of typical occupancy [20]. Air change rates are a function of outside air infiltration and mechanical ventilation in comparison to house volume. The recommended rate is meant to handle the daily moisture load produced by a typical family, prevent mould growth and reduce other airborne contaminants. A five person family releases 15 kg·day⁻¹ water vapour [29].

In general, homes built after 1980 in Ottawa are at high risk of moisture damage if used as MGOs. Air change rates much higher than those normally found in new homes would be required to tolerate the additional moisture. Many Windsor homes (41%) had air change rates below the recommended standard and would be unable to handle more than one or two house plants (Table 1). The additional moisture released by 100 plants would result in mould growth in all the Windsor homes. The average air change rate for Windsor homes tested was 0.45 ac·h⁻¹ (range 0.11–1.98 ac·h⁻¹), at this rate ∼16 plants could be theoretically tolerable. Data collected from Regina homes showed a similar trend. Many homes (38 of 103, i.e. 37%) were inadequately ventilated. Air change rates ranged from 0.072 to 3.02 ac·h⁻¹ with a median of 0.463 ac·h⁻¹. Of all 103 homes tested, only eight could theoretically tolerate the moisture released by >100 marijuana plants, assuming that the home did not have an existing mould problem. On average, houses in Regina could theoretically tolerate 31 marijuana plants; however, when homes with air change rates above 1 ac·h⁻¹ (7 homes) are excluded, the number of home drops to 19 (data not shown), comparable to Windsor data.

Table 1.

Maximum tolerable number of marijuana plants for houses in Windsor, ON

No.	Air change rate (ac·h⁻¹)	House volume (m³)	Maximum tolerable number of marijuana plants
1	0.105	680	^a
2	0.106	566	^a
3	0.118	1019	^a
4	0.121	657	^a
5	0.147	498	^a
6	0.162	521	^a
7	0.167	566	^a
8	0.174	770	4
9	0.185	612	^a
10	0.186	634	^a
11	0.225	748	14
12	0.227	680	10
13	0.243	634	10
14	0.244	634	10
15	0.247	453	^a
16	0.253	408	^a
17	0.256	453	^a
18	0.258	177	^a
19	0.258	408	^a
20	0.269	295	^a
21	0.271	453	1
22	0.286	362	^a
23	0.311	181	^a
25	0.336	634	27
26	0.337	725	36
27	0.347	544	20
28	0.354	227	^a
29	0.355	222	^a
30	0.369	227	^a
31	0.422	476	24
32	0.427	725	55
33	0.466	227	^a
34	0.468	295	^a
35	0.482	283	5
36	0.495	453	30
37	0.513	227	^a
38	0.521	215	^a
39	0.527	430	31
40	0.535	680	71
41	0.544	340	19
42	0.549	340	19
43	0.553	453	38
44	0.556	630	67
45	0.571	680	78
46	0.571	385	29
47	0.595	906	122
48	0.603	362	29
49	0.612	249	9
51	0.650	272	17
52	0.657	272	17
53	0.697	261	18
54	0.723	204	8
55	0.748	283	27
56	0.877	227	23
57	0.923	396	72
58	0.934	204	21
59	1.982	227	96
Average	0.442	451	19

Note: ^aExisting risk to moisture problems.

These estimates cannot include the moisture released from drying. To assess this, the presence of mould on the product was used as an indicator of the percentage that is not dried properly (which would demonstrate the use of an appropriate drier indoors). Most samples (>90%) of dried marijuana test showed evidence growth of the allergenic and opportunistic pathogens such as Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Mucor species, and various Penicillium species. In most samples tested, mould contamination was high (10⁴–10⁷ CFU·g⁻¹) [30 –33].

Discussion

Infiltration was essentially the sole source of air change within Canadian homes built before World War II (WWII). These poorly insulated, air leaky homes have (or had) air change rates well above 0.3 ac·h⁻¹. Since WWII, however, there has been a need for greater energy efficiency and hence better insulation in homes. To maintain air change rates, mechanical ventilation was developed; however, many new homes have been left with inadequate ventilation [20].

Leaves of all plants bear various phylloplane fungi. The spores of these dominate outdoor air during the growing season and primarily comprise the fungus Alternaria alternata and a number of species of Cladosporium, but mainly Cladosporium herbarum and Cladosporium cladosporioides. A large percentage of the population is allergic to these fungi [34]. A. fumigatus grows and dominates on decaying vegetation under warm conditions or where biological heating has taken place, including piles of leaves or compost. It is cellulolytic on delignified materials including leaves as well as paper and fabrics. The prevalence of A. fumigatus contamination of marijuana resulting from growing, harvesting, or smoking marijuana poses a health risk. These risks include allergic reactions [13,35]. Aside from respiratory disease, those allergic individuals with chronic high exposure may also develop allergic bronchopulmonary aspergillosis or ABPA [35,36]. A. fumigatus infections have also been reported in marijuana-exposed populations [37 –41].

Dales et al. [8] note that apart from floods, there are four major sources of mould growth in residences: leaks in building fabric (rare in Canada because it is cold to very cold in winter and for the particular reason noted previously, uncommon in MGOs), ventilation failure leading to condensation, unattended plumbing leaks and household mould (e.g. mould growth on kitchen and bathroom surfaces, hidden food spills, etc.). Some degree of mould damage is present in ∼30% of Canadian homes [42,43]. Inadequate ventilation for the internal moisture sources in a house accounts for most mould growth [9,10]. As noted, field experience indicates that mould damage in MGOs is often extensive [3 –6].

Reviews by cognizant authorities, Health Canada (2004) [22], INSPQ (2002) [23], the Institute of Medicine, US National Academy of Sciences [24,25], an expert panel of the United States Centers for Disease Control/National Center for Healthy Homes [26] and the World Health Organization [26] emphasize the effects on population health of mould in the context of building dampness. These include increased allergic and upper respiratory disease. Health Canada [44] and Krieger et al. [26] state that there is sufficient evidence for health benefit from remediation of mould and dampness. Fungi are associated with new onset asthma in both adults and children and with non-atopic asthma [45,46].

The field data that exist reveal a number of poorly quantified abiotic factors. The cultivation of marijuana requires the large-scale use of liquid fertilizers, insecticides and fungicides [3,4,6] not authorized for indoor use. Residues of the pesticides are detected on marijuana [33]. It is common for operators of detected MGOs in Vancouver to disconnect the furnace and re-vent the exhaust into the grow area to increase the carbon dioxide concentration (60% of detected MGOs) [4]. Virtually, all these houses had illegal wiring, and by-passes to the electrical meters [3,4]. Aside from the potential for CO poisoning, heating is also done with unvented combustion appliances thus increasing NO₂ and particulate exposures which are harmful to respiratory health [8]. There has been little systematic study of these contaminants.

From Ontario to British Columbia, the large majority of MGOs are occupied by families including children [3,4,47]. It is reasonable to anticipate that this is also the case in the USA. In response, Alberta enacted the Drug-Endangered Children Act. This legislation states that children exposed to an environment where manufacturing occurs, may need protection on health grounds. In the rest of Canada, Medical Officers of Health, the Provincial Health Department, and other authorities can act to protect child health. Documenting the environmental conditions is required before taking any legal action.

Of particular concern is that at least one-third of Canadian homes could not theoretically tolerate the additional water vapour released by marijuana plants. Considering the number of plants found at illegal MGOs (and MMAR), few, if any, homes in the cities examined would be able to tolerate additional moisture. There are few data on ventilation rates in multi-unit apartment buildings. However, the available data suggest that they are likely lower than assumed and that odour transfer problems are not uncommon [48,49]. Again, this assumes that the home or apartment does not have an existing mould problem, which is an uncertain assumption. Both US and Canadian studies indicate that the attributable risk for asthma and respiratory disease from mould growth in homes is on the order of 20% [50,51]. Some risk to population health is associated with exposure to A. fumigatus and is related to the extent of marijuana drying that is done in a MGO. In the case of marijuana production under MMAR, houses and apartments would have to be evaluated on a case by case basis and special rooms built to permit the cultivation of the plant indoors.

It is important to note that well-maintained house plants (which are much smaller than marijuana plants) are not a particular risk. The assumption has been made that homes have fewer than three plants [29]. However, as the number increases and if the plants are not well maintained, this can increase both moisture burdens and the growth of A. fumigatus [52].

Conclusion

When addressing situations where families are discovered living in MGOs resulting from police action as well as public concerns of the inadvertent purchaser of undetected former MGOs, primary care physicians and municipal public health officials need to be aware of the issues discussed in this paper. These include (1) the cultivation of marijuana typically leading to moisture and mould problems, (2) risk of unusual exposures to A. fumigatus and, potentially, (3) chemical residues. Similarly, more information on these hazards may be needed for industrial hygienists, home inspectors, police and other first responders and public health officials in Canada and the USA.

Footnotes

Acknowledgments

This review was funded by Health Canada and an NSERC IRC to JDM. Helpful reviews were provided by Don Fugler PEng, Mark Lawton PEng, Morrison Hershfield, Ltd., and Richard Summerbell PhD (University of Toronto, Sporometrics, Ltd.). It is based on a larger report for Health Canada. Comments from two anonymous reviewers are appreciated.

References

Royal Canadian Mounted Police National Conference: Illegal Marihuana Grow Operations Post Conference Report, Royal Canadian Mounted Police, Ottawa, ON, 2004.

United Nations Office on Drugs and Crime (UNODC): World Drug Report for 2007, United Nations Publications, Geneva, 2008.

OACP: Green Tide: Indoor marijuana cultivation and its impact on Ontario. Ontario Association of Chiefs of Police, 40 College Street, Toronto, ON, 2003.

Douglas

: The Health and safety of children living in marijuana grow operations: A child welfare perspective. PhD thesis, School of Social Work, University of British Columbia, 2010. Available at: https://circle.ubc.ca/handle/2429/25751 (accessed May 7, 2011).

D’Halewyn

M-A

: Contamination des maisons utilisée pour la culture de marijuana par les moisissures, Vol. 17, Quebec, QC, Bulletin d’Information en santé environmental (INSPQ), 2006, pp. 6–10.

Salares V, Dyck M: Research highlight: A discussion paper on indoor air quality investigations of houses used for marijuana grow operations, Canada Mortgage and Housing Corporation, Ottawa, ON, Technical series: 07-101, 2007.

Government of Canada: Medical marihuana access regulations SOR/2001-27 pursuant to the Controlled Drugs and Substances Act s.c.1996, c.19, ss55(1), Government of Canada, Ottawa, ON, 2001.

Dales

Liu

Wheeler

Gilbert

: Quality of indoor residential air and health: Can Med Assoc J 2008;179:147–152.

Lawton

Dales

White

: The influence of house characteristics in a Canadian community on microbiological contamination: Indoor Air 1999;8:2–11.

10.

Prezant

Weekes

Miller

: Recognition, Evaluation and Control of Indoor Mold, Sections 5, 7.1, 7.11. Fairfax, VA, American Industrial Hygiene Association, 2008.

11.

ASHRAE: Indoor Air Quality Guide: Best Practices for Design, Construction, and Commissioning. Atlanta, GA, ASHRA Engineers, 2009.

12.

Prezant

Weekes

Miller

: Recognition, Evaluation and Control of Indoor Mold, Section 4. Fairfax, VA, American Industrial Hygiene Association, 2008.

13.

Flannigan

Samson

Miller

: Microorganisms in Home and Indoor Work Environments: Diversity, Health Impacts, Investigation and Control, 2nd edn, Boca Raton, FL, CRC, 2011.

14.

International Energy Agency: A Sourcebook, Report Annex XIV. Leuven, Belgium, International Energy Agency, 2006.

15.

Brands

: Systema Naturae 2000. Amsterdam, The Netherlands, 1989-2005. Available at: http://sn2000.taxonomy.nl/ (accessed September 19, 2010).

16.

Kaa

: Cannabis plants illicitly grown in Jutland (Denmark): Z Rechtsmed 1989;102:367–375.

17.

Christian JE: A Search for Moisture Sources: Bugs Mold & Rot II: Workshop Proceedings, National Institute of Building Sciences, Washington, DC, November 16–17, 1993, pp. 71–81.

18.

Muller

Heindl

: Drying of medicinal plants: in Bogers

Craker

Lange

(eds): Medicinal and Aromatic Plants, New York, Springer, 2006, pp. 237–252.

19.

Kovesi

Gilbert

Stocco

Fugler

Dales

Guay

Miller

: Indoor air quality and the risk of lower respiratory tract infection in young Canadian inuit children: Can Med Assoc J 2007;177:155–160.

20.

Reardon J, Fugler D: Assessment of natural ventilation for Canadian residential buildings, Canada Mortgage and Housing Corporation, Ottawa, ON, Technical series 08-100, 2008.

21.

Miller

Dugandzic

Frescura

A-M

Salares

: Indoor and outdoor-derived contaminants in urban and rural homes in Ottawa: Canada: J Air Waste Manage Assoc 2007;57:297–302.

22.

Health Canada: Fungal Contamination in Public Buildings: Health Effects and Investigation Methods. ON, Health Canada, 2004, ISBN 0-662-37432-0.

23.

INSPQ: Les risques à la santé associés à la présence de moisissures en milieu intérieur. Québec, QC, Institut national de santé publique du Québec, 2002.

24.

NAS: Clearing the Air: Asthma and Indoor Air Exposures. Washington, DC, National Academy Press, Institute of Medicine, National Academy of Sciences, 2000.

25.

NAS: Damp Indoor Spaces and Health. Washington, DC, National Academies Press, Institute of Medicine, National Academy of Sciences, 2004.

26.

Krieger

Jacobs

Ashley

Baeder

Chew

Dearborn

Hynes

Miller

Morley

Rabito

Zeldin

: Housing interventions and control of asthma-related indoor biologic agents: A review of the evidence: J Public Health Manage Pract 2010; 16:s11–s20.

27.

WHO: Guidelines for Indoor Air Quality: Dampness and Mould. DK-2100 Copenhagen, Denmark, WHO Regional Office for Europe, ISBN 978 92 890 4168 3, 2009.

28.

Klimisch

Andreae

Tillmann

: A systematic approach for evaluating the quality of experimental toxicological and ecotoxicological data: Regul Toxicol Pharmacol 1997; 25:1–5.

29.

TenWolde

Walker

: Interior moisture design loads for residences: in Buildings VIII: Performance of Exterior Envelopes of Whole Buildings; VIII: Integration of Building Envelopes, Atlanta, GA, ASHRAE, 2001, ISBN: 1883413966.

30.

Kurup

Resnick

Kagen

Cohen

Fink

: Allergenic fungi and actinomycetes in smoking materials and their health implications: Mycopathologia 1983;82:61–64.

31.

Verweij

Kerremans

Voss

Meis

JFGM

: Fungal contamination of tobacco and marijuana: JAMA 2000;284:2875.

32.

Kagen

Kurup

Sohnie

Fink

: Marijuana smoking and fungal sensitization: J Allergy Clin Immunol 1982;71:389–393.

33.

McLaren

Swift

Dillon

Allsop

: Cannabis potency and contamination: A review of the literature: Addiction 2008;103: 1100–1109.

34.

Horner

Helbling

Salvaggio

Lehrer

: Fungal allergens: Clin Microbiol Rev 1995;8:161–179.

35.

Gibson

: Allergic bronchopulmonary aspergillosis: Semin Respir Crit Care Med 2006;27:185–191.

36.

Llamas

Hart

Schneider

: Allergic bronchopulmonary aspergillosis associated with smoking moldy marijuana: Chest 1978; 73:871–872.

37.

Hii

Tam

JDC

Thompson

Naughton

: Bullous lung disease due to marijuana: Respirology 2008;13:122–127.

38.

Wallace

Lim

Browdy

Hopewell

Glassroth

Rosen

Reichman

Kvale

: Risk factors and outcomes associated with identification of Aspergillus in respiratory specimens from persons with HIV disease: Chest 1998;114:131–137.

39.

Szyper-Kravitz

Lang

Manor

Lahav

: Early invasive pulmonary aspergillosis in a leukemia patient linked to Aspergillus contaminated marijuana smoking: Leuk Lymph 2001;42:1433–1437.

40.

Sutton

Lum

Torti

: Possible risk of invasive pulmonary aspergillosis with marijuana use during chemotherapy for small cell lung cancer: Drug Intell Clin Pharm 1986;20:289–291.

41.

Cescon

Page

Richardson

Moore

Boerner

Gold

: Invasive pulmonary aspergillosis associated with marijuana use in a man with colorectal cancer: J Clin Oncol 2008;26:2214–2215.

42.

Dales

Zwanenburg

Burnett

Franklin

: Respiratory health effects of home dampness and molds among Canadian children: Am J Epidemiol 1991;134:196–203.

43.

Dales

Ruest

Guay

Marro

Miller

: Residential fungal growth and incidence of acute respiratory illness during the first two years of life: Environ Res 2010;110:692–698.

44.

Health Canada: Residential indoor air quality guidelines: moulds. Ottawa, Ontario, Canada, 2007. Available at: http://www.hc-sc.gc.ca/ewh-semt/pubs/air/mould-moisissure-eng.php (accessed December 5, 2007).

45.

Cox-Ganser

White

Jones

Hilsbos

Storey

Enright

Rao

Kreiss

: Respiratory morbidity in office workers in a water-damaged building: Environ Health Perspect 2005;113:485–490.

46.

Jaakkola

Hwang

Jaakkola

: Home dampness and molds, parental atopy, and asthma in childhood: A six-year population-based cohort study: Environ Health Perspect 2005;113:357–361.

47.

Plecas D, Malm A, Kinney B: Marihuana growing operations in British Columbia revisited (1997-2003), Department of Criminology and Criminal Justice, University of the Fraser Valley, Abbotsford, 2005.

48.

CMHC: Air leakage characteristics, test methods and specifications for large buildings, Canada Mortgage and Housing Corporation, Ottawa, ON, Technical Series 01-123, 2001.

49.

CMHC: Solving odour transfer problems in your apartment, Canada Mortgage and Housing Corporation, Ottawa, ON, Available at: http://www.cmhc-schl.gc.ca/en/co/reho/reho_002.cfm (accessed September 19, 2010).

50.

Fisk

Lei-Gomez

Mendell

: Meta-analyses of the associations of respiratory health effects with dampness and mold in homes: Indoor Air 2007;17:284–296.

51.

Dekker

Dales

Bartlett

Brunekreef

Zwanenburg

: Childhood asthma and the indoor environment: Chest 1991;100:922–926.

52.

ASHRAE: Strategy 2.6 – Indoor and Outdoor Plants that may affect IAQ. Indoor Air Quality Guide: Best Practices for Design, Construction, and Commissioning. 1791 Tullie Circle, Atlanta, GA, 30329, American Society of Heating, Refrigeration & Air-Conditioning Engineers, 2009.