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Year : 2017  |  Volume : 10  |  Issue : 4  |  Page : 966-972
Method for assessment of indoor household dampness for its use in epidemiological studies in tropical settings

1 Department of Environmental Health Engineering, Sri Ramachandra University, Chennai, Tamil Nadu, India
2 Department of Microbiology, Sri Ramachandra University, Chennai, Tamil Nadu, India

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Date of Web Publication5-Oct-2017


Objectives: Epidemiological studies are available in developed countries with temperate conditions that assessed residential dampness in relation to health using various methods, but studies are very limited in tropical settings, especially in developing countries though favorable conditions prevail. As the reasons for building dampness in tropics are not similar to Western countries, there is always a need for baseline information on its prevalence and selection of method for assessment. Methods: We here discuss on limitations and advantages of each of the various methods to assess dampness. In addition, based on a household level survey on the possible sources of dampness and condition prevailing, we have developed a study instrument for obtaining self-reported information related to residential dampness that is suitable for epidemiological studies in a tropical developing country. Conclusion: Based on the suitability of the methods discussed, it is concluded that a single method would not be valid enough to provide accurate results in regions where previous studies are unavailable. A combination of objective measurement and self-reported information would be appropriate to assess dampness in health-related epidemiological studies conducted in tropical developing countries that lack sufficient previous research. This study may act as a prelude for further large level-field investigations on dampness in tropical developing countries.

Keywords: Assessment method, dampness, developing countries, tropical countries

How to cite this article:
Manivannan S, Venugopal V, Kindo AJ, Kuppuswamy R. Method for assessment of indoor household dampness for its use in epidemiological studies in tropical settings. Ann Trop Med Public Health 2017;10:966-72

How to cite this URL:
Manivannan S, Venugopal V, Kindo AJ, Kuppuswamy R. Method for assessment of indoor household dampness for its use in epidemiological studies in tropical settings. Ann Trop Med Public Health [serial online] 2017 [cited 2021 Apr 14];10:966-72. Available from:

   Introduction Top

According to the WHO guidelines “any visible, measurable or perceived outcome of excess moisture that causes problems in households, such as mould, leaks or material degradation, mold odor or directly measured excess moisture (in terms of relative humidity or moisture content or microbial growth) are called dampness.”[1] Knowledge regarding the root cause of dampness prevailing in that geographical region would help researchers in the selection of the appropriate method for its assessment.

Dampness in houses encourages the colonization of molds that further gets enriched by the nutrients available in the buildings and after complete maturation disperses spores into the air that is suggested to be a strong, consistent indicator of risk of asthma, and other respiratory symptoms. Studies on dampness and its relation to health are numerous in temperate and developed countries and reported dampness that varied from 20% to 50%.[2],[3] They also estimated significant association between dampness and respiratory health. Studies in tropical developed countries indicated higher prevalence of dampness and stronger association with respiratory health but very limited.[4],[5] The WHO guidelines on indoor dampness and mold, (2009) estimated the prevalence of dampness to affect 10%–50% of indoor environments in developing countries. It also emphasized the need for larger field studies that examine dampness in relation to health outcomes in developing countries as studies are very limited.[1] In a developing, climatic conditions, diversified housing characteristics and poor housing conditions, lack of affordability for the building owners for remediation are favorable to initiate and accelerate the dampness and mold proliferation.[6],[7]

The previous studies mostly assessed dampness based on self-reported questionnaires.[8],[9] Few studies discussed the reporters and interviewers bias in the use of questionnaire.[10] To overcome the problem of bias, a limited number of studies measured the indicators of dampness in several other ways using moisture meter on walls and floor,[11],[12] using other indoor air quality (IAQ) parameters,[13] or by surveyor assessment.[14],[15] Few studies used a combination of moisture meter graded moisture percentage as well as questionnaire to collect information on dampness and related it to health.[16] Few researchers used a combination of more than two methods to overcome the limitations of individual method in assessing dampness.[17]

The lack of robust study methods in developing countries with tropical climates makes it hard to adopt a particular method to assess residential dampness. Hence, there is an urgent need to find or develop a suitable method to assess indoor dampness in developing countries where the conditions for dampness are much favorable. Hence, this study aimed at selecting a suitable method for dampness assessment by discussing the advantages and limitations of methods available and to derive a suitable study instrument (questionnaire) for dampness assessment in tropical developing countries.

   Methods of Dampness Assessment Top

Different methods for dampness assessment have been used across the globe in various climatic settings, buildings with varied materials, varied fuel usage, aged buildings, etc. Few methods are being discussed here for its suitability of use in tropical developing country. The methods are classified as shown in [Figure 1].
Figure 1: Classification of methods used to assess dampness in residential buildings

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Objective assessment of dampness

Objective assessment can be qualitative or quantitative in its assessment can arrest interviewer and participant's bias created during questionnaire administered. However, this cannot provide the retrospective information related to dampness.

Qualitative methods

Plastic sheet method

As addressed in ASTM D4263-83 (2005),[18] Standard Test Method for Indicating Moisture in Concrete is by the plastic sheet method. This is a nondestructive test where perimeter of the plastic sheet will be firmly taped to the wall overnight. At the end of exposure (after 24 h), underside of the sheet and surface of the concrete will be examined visually for the presence of moisture. The method has not been used in recent studies due to its inherent limitations.

Passive infrared thermography

This method detects anomalies due to moisture in buildings using the thermal properties of water. In water damaged areas, the heat capacity of the material is greater than the dry material resulting in a condition that the water damaged area will be quite warmer or cooler than the surrounding area. This difference is captured using an infrared camera which converts the spatial variations of infrared radiance from a building surface into a two-dimensional image called thermogram displayed as a range of colors or tones. This can be used for moisture mapping. The method is nondestructive and fast compared to other objective methods as wide area can be scanned at a time.[19]

Quantitative assessments

Moisture meter

Moisture meter measures dampness in terms of percentage of moisture and the houses can thus be graded as dry, moderate, and severe in terms of the level of dampness. An electric resistance type moisture meter can be used to find the moisture percentage on the wall material. Readings will be taken at three points (middle and either ends) of the wall just above the skirting board. The worst percentage of dampness (highest percentage) will be recorded as measures of severity of dampness for that housing.[11]

Assessment of measurable indoor air quality parameters

A combination of relative humidity, indoor temperature, and ventilation are other alternative measures that can be considered. In general, buildings with high levels of relative humidity (>70%), temperature between 10°C and 40°C, and poor ventilation are required for growth and proliferation of indoor fungi.[5] Hence, the variables within these limits are considered as surrogate indicators of dampness.

Gravimetric method

Few grams of the building material are collected from the desired depth of the building structure. This is kept in the air tight container to avoid evaporation till weighing. The material is weighed before and after drying in the oven at 105°C. The moisture quotient is then calculated.[20]

Calcium carbide method

The sample is taken from the damaged area, weighed, kept in a gas pressure vessel with calcium carbide ampoule, and some steel balls. The vessel is shaken to break the ampoule releasing the calcium carbide to react with the moisture content in the sample. The resulting gas pressure is detected by a gauge at the top of the vessel. The reading is directly proportional to the moisture content of that material. The moisture quotient corresponding to the moisture pressure can be measured using conversion table depending on the sample material.[20]

Surveyor assessment

Some studies assess dampness in the study households with the help of a panel of trained inspectors. Each of the rooms will be visually inspected for signs of mold or water damage. The location of the damage, discoloration of the surface material, and size of the damaged area will be recorded by the inspectors. Tape samples will be collected from the damaged surfaces for further microscopic examination. The house will be categorized as none, low, and high based on the extent of water damage and visible mold.

Questionnaire-based self-reported household dampness

A properly framed questionnaire can elicit information on all types of dampness and the actual source and extent of water damage, namely, poor building construction, pipe leakage, floor ooze, and water drained in the surroundings,. Questions related to dampness are retrospective in nature that collects relevant information for the past few years. Questions used by different studies in different regions for the assessment of dampness and definition of the symptoms are given in [Table 1].
Table 1: Questions used to assess dampness and definition of the symptoms used by various studies in different geographic conditions

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Irrespective of the region, the most common questions used by various studies were about the moisture stain, mold odor, and the visible mold. Additional questions can be framed based on the conditions prevailing in those geographical regions. The common questions would be:

  1. “Have there been any incidences of moisture stains in the wall during the last 1–2 years in your house?”
  2. “Was there any perception of pungent, moldy, musty, or stuffy odor in your dwelling in the last 1–2 years?”
  3. “Did you have any occurrence of visible mold in your home in the last 1–2 years?”

The previous studies done in the geographical zone with similar climatic conditions must be used as starting point for questionnaire preparation with further customization of the questionnaire to collect relevant information.

The need for a customized questionnaire for tropical setting

Although few studies in tropical settings that reported dampness are available, a study instrument is needed exclusively that can be best applicable in tropical developing countries that has diverse climatic zones and conditions.

Prevailing condition in India

The climatic condition of India and household environment is diverse with numerous sources for dampness [Figure 2]. India experiences a wide range of climatic conditions, high relative humidity, varied household types, various fuel usage, improper remediation measures, and unhygienic conditions responsible for developing indoor dampness in buildings.
Figure 2: Common sources of indoor dampness in Indian household. (a) Unhygienic conditions (b) poor building construction s unfurnished walls or leaky roofs or poor joints (c) floor ooze (d) leaky pipelines (e) improper drainage system (f) age of the building

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Household survey

A questionnaire-based study conducted in 700 houses (included rural and urban houses) in Tamil Nadu, India to collect information on the major sources of household dampness had its challenges in satisfying the objectives of the study using the existing questionnaire. The reported dampness in about 353 homes and the perceptions of dampness as reported by the residents was very subjective. As represented in [Figure 3], the reasons given as sources of building dampness included poor construction, leakage in water pipelines, improper drainage system, water logging, age of the building, and unhygienic conditions. The reasons and perceptions varied widely among the participants in ascertaining causalities for household dampness. Such subjective data are less value added for epidemiological studies.
Figure 3: Reasons reported by the residents of the households (in percentage) in Tamil Nadu

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Based on the conditions that prevail in tropical settings, existing survey reports and previous literature on dampness assessment methods, questions are framed in addition to the three common questions mentioned above. The additional questions will potentially elicit information that could be used to inform city, state or regional information on household dampness. The framed questions include the following:

  • “Give the reasons of dampness in your house” (participant are helped with options, and they are allowed to choose multiple reasons also)
  • “Did you have water leakage in your home during the last 2 years?”
  • “Did water ooze from the floor during the last 2 years?”
  • “Did you have any occurrence of flooding in your house within the last 2 years”
  • “Do you have damage in the sleeping area due to dampness?”
  • Do you have any water bodies near your residence that could influence dampness in your home?
  • How do you perceive your area of residence in terms of influencing dampness in your home? (options included “mild,” “moderate,” “severe”)
  • What is your perception about dampness between seasons (summer/winter/rainy)?
  • Does dampness, if any, impact your thermal comfort in your household?
  • Have you had any material and/or property damage due to dampness?
  • The general rating of dampness in their house by the participant can also be made using the question “please rate the moisture problem in your house” (options included “mild,” “moderate,” “severe”)
  • How have you addressed the dampness problem in your residence, if any?

A positive response to the above-mentioned questions may indicate dampness in some form in the household. In addition, the questionnaire gives related information on dampness to know its severity and participant's rating of dampness.

   Discussion Top

Studies that use plastic sheet method for dampness assessment is very limited and have no use in low socioeconomic countries residences with mud walls. Passive infrared thermography method though less time-consuming may not be practically applicable for individual houses in large-scale assessments in epidemiological studies.[19] Objective quantitative assessments of moisture using moisture meter gives percentage of dampness at the surface but could read only moisture present at the time of sampling [11],[12] and does not reveal the conditions that prevailed in that house during the previous years. Assessments of IAQ parameters are considered to be easier, but remain to be surrogate and do not actually measure the moisture content. This can be used only in resource-limited situations and cannot be relayed as exact assessment. The other two methods; gravimetric and calcium carbide method are invasive in nature and may find less acceptance in population-based studies as they are slow and indirect, respectively. Surveyor assessment, a robust, and reliable method can prove expensive and has lot of practical limitations in epidemiological studies even though this method could extract valuable results.

Self-reported assessment for dampness using questionnaire always extracts present and retrospective information.[8],[9],[23][24],[25],[26] It also collects other-related information on dampness. However, the definition of the symptoms may depend on the conditions prevailing in that geographic region. A robust questionnaire assessment requires the interviewer to have a good knowledge regarding dampness and its implications on the property, residents' comfort, and health. The main limitation of the information obtained through self-reported questionnaires is inherent interviewer or participant bias, which could be avoided by framing specific questions after a detailed survey.

   Conclusion Top

Since no one method could be perfect and give accurate information on household dampness, a combination of self-reported information and objective quantitative measurement (using moisture meter) of dampness would be most suitable for diversified conditions prevailing in tropical developing countries. Dampness is a looming public health issue that has merited less attention in developing countries and the implications of household dampness is not only limited to material and property dampness, but also has major implications on the health, comfort, and well-being of the residents. Further studies to develop robust methods to assess household dampness are urgently needed. Generating zone-wise or region-wise reliable data on household dampness can inform planning authorities to address the issue in an informed and planned manner.


Authors thank the technical guidance provided by Dr. Kalpana Balakrishnan, Director, SRU-ICMR Center for Advanced Research on Air Quality, Climate and Health (SRU-CAR), Dr. S. Sankar, HOD, Department of Environmental Health Engineering, SRU and members of the ICMR-CAR Advisory Committee, for the conduct of the field work.

Financial support and sponsorship

Funded by the Indian Council of Medical Research (ICMR).

Conflicts of interest

There are no conflicts of interest.

   References Top

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Correspondence Address:
Saraswathy Manivannan
Department of Environmental Health Engineering, Sri Ramachandra University, Porur, Chennai, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ATMPH.ATMPH_298_17

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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