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Research article

Normal background levels of air and surface mould reserve in English residential building stock: A preliminary study towards benchmarks based on NAHA measurements

Authors
  • Yasemin Didem Aktas orcid logo (University College London (UCL), Department of Civil, Environmental and Geomatic Engineering (CEGE), Epicentre Research Group, London WC1E 6DE, UK)
  • Morten Reeslev (Mycometer A/S, Dr Neergaards Vej 3, 2970 Hørsholm, Denmark)
  • Hector Altamirano orcid logo (UK Centre for Moisture in Buildings (UKCMB), University College London, London WC1H 0NN, UK)
  • Neil May (UK Centre for Moisture in Buildings (UKCMB), University College London, London WC1H 0NN, UK)
  • Dina D’Ayala orcid logo (University College London (UCL), Department of Civil, Environmental and Geomatic Engineering (CEGE), Epicentre Research Group, London WC1E 6DE, UK)

This is version 2 of this article, the published version can be found at: https://doi.org/10.14324/111.444/ucloe.000005

Abstract

This paper reports results obtained from a surface (both visually clean and dirty/dusty surfaces) and active (aggressive or activated) air testing scheme on 140 residential rooms in England, without visible water damage or mould growth, along with a few rooms with visible mould growth/water damage tested for comparison purposes. The aim was to establish normal background levels of mould in non-water-damaged interiors to benchmark a ‘normal’ indoor environment, and in turn when there is a need for further investigation, and, possibly, remediation. Air and surface mould was quantified based on the activity of β-N-acetylhexosaminidase (EC 3.2.1.52; NAHA). The obtained readings showed a log-normal distribution. Ninety-eight percent of the samples obtained from visually clean surfaces were equal to or less than 25 relative fluorescence units (RFU), which is suggested to be the higher bound for the range which can be used as a success criterion for surface cleaning/remediation. Of samples obtained from visually dirty/dusty surfaces, around 98% were below 450 RFU, which is suggested to define the lower-bound for abnormally high levels of mould, rare even on dirty/dusty surfaces. Similarly, around 98% of the air samples were found to have 1700 RFU or below. Values above 1700 RFU are therefore deemed unlikely in a non-problem indoor environment and can be indicative of a possible problem inducing mould growth. The samples with values below 1700 were further divided into three proposed sub-categories. Finally, the obtained RFU values and the suggested benchmarks were compared to those obtained from 17 non-residential indoor environments tested previously in Copenhagen, and the benchmarks that are currently used in Danish national standards, and they were both found to be highly congruent, suggesting that local climate regimes and room functions might not be as influential on indoor mould levels as commonly thought, or that the nuances between England and Denmark in terms of these factors are not strong enough to lead to sizable changes in the typical indoor mould levels in these countries’ building stocks.

Keywords: mould, surface sampling, active (aggressive or activated) air sampling, NAHA, England, Denmark

Rights: © 2020 The Authors.

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1Citations

Published on
06 Mar 2020
Peer Reviewed
License
Creative Commons Attribution 4.0

 Open peer review from Ulf Thrane

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-ENG.AAJUPL.v1.RGANCF
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Engineering , Civil engineering , Environmental engineering , Microbiology & Virology , Life sciences
Keywords: surface sampling , NAHA , mould , Environmental science , Sustainability in architecture and the built environment , UK , Denmark , active (aggressive) air sampling

Review text

The authors have chosen to use a single method for determination of mould, the quantification of the N-acetylhexoaminidase (NAHA) activity supported by microscopy of the filter used for the NAHA activity determination. The limitation is that the use of NAHA activity determination is not a worldwide standard. Furthermore, the results are impossible to compare to results obtained from more widespread methods being agar based contact plates or air-samplers of the impact type using Petri dishes. Still the present manuscript is an important step forward.

Comments:

General: When citations are (author, year) the list of references should be alphabetical and not in order of appearance as now.

Page 2: The citations ‘Statens Byggeforskningsinstitut 2003 a&b’ should rather be (Valbjørn, 2003; Koch and Nielsen, 2003), respectively. The references are:

  • Valbjørn O. 2003. Undersøgelse og vurdering af fugt og skimmelsvampe i bygninger (By og Byg Anvisning 204). Hørsholm: Statens Bygge­forskningsinstitut. Localised 3 rd of September 2019 at http://anvisninger.dk/204
  • Koch AP, Nielsen PA. 2003. Renovering af byg­ninger med skimmelsvampevækst (By og Byg Anvisning 205). Hørsholm: Statens Bygge­forskningsinstitut. Localised 3 rd of September 2019 at http://anvisninger.dk/205

Page 2, Section 2, first line: How were the 140 non-water damaged homes classified as such? Measurement of relative humidity? Humidity in construction parts?

Page 3, Study site: Any reason for the distribution between type and age of buildings?

Page 4, last paragraph, line 2: bad reference to a figure(?).

Page 4, last paragraph, line 4: “17 properties in Denmark”? Not mentioned in Materials and Methods! New data, or already published data? If published, a citation to publication is needed.

Page 5, paragraph marked (4): it was not the Danish Building Research Institute (= Statens Byggeforskningsinstitut) that brought forward the limits 25 RFU and 450 RFU, respectively. It was the private company Mycometer A/S, as clearly presented in 2003 publication from Statens Byggeforskningsinstitut. You need to find the background information for the use of these RFU levels, as it is not clear why you choose to use 25 and 450. How is the distribution of all your RFU readings? Mean and median values?

Page 6, first line below figure 2: “…1700 RFU are most likely indicative…”. It is a very fluffy argument, why not choose 1500, or 2000? How is the distribution of all your RFU readings? Mean and median values?

Page 7, Section 4 (Discussion): is not really a discussion – and Section is “Results and Discussion” – Section 4 is rather some concluding remarks. Rephrase and integrate into Section 3 or 5.1

Page 7, Paragraph numbered (2): A citation is needed to direct the reader to information about the Danish study. Where has it been published?

Page 8: It is recommended to show some statistical evidence for the RFU benchmarks presented.



Note:
This review refers to round 1 of peer review.