W.Y. Chan

Thermal Environmental Interference with Airborne Bacteria and Fungi Levels in Air-Conditioned Offices

Indoor airborne bacteria and fungi levels can be selected as indicators of a healthy indoor environment. This study investigated the relationships between the airborne bacteria levels, fungi levels, and thermal environmental parameters, i.e., air temperature and relative humidity, in some offices with a Mechanical Ventilation and Air-Conditioning (MVAC) system operating. A total of 101 samples were collected from two typical Hong Kong air-conditioned office premises. There was evidence that the operation of the MVAC system would have significant influence on both of the indoor airborne bacteria and fungi levels. The results showed that no significant difference in airborne bacteria and fungi levels was observed between offices having similar thermal environments ( p > 0.05). However, significantly higher airborne bacteria and fungi levels were found in the same office during non-office hours when the air-conditioning system was shut down ( p<0.03). It was also reported that the airborne bacteria and fungi levels would be correlated with the thermal environmental parameters in some offices ( p<0.0001).

An Assessment of Airborne Fungi Exposure Risk Level in Air-conditioned Offices:

The exposure to airborne fungi has not been included in many regular indoor air quality (IAQ) assessments of air-conditioned (A/C) offices. This study examined the feasibility of using a proposed relative index of fungal exposure (RIFE) as a quantitative measure to specify the enclosure effect of an indoor environment in 82 Hong Kong A/C offices. The airborne fungi count ranged from 2 to 92CFU·m -3. Yeast, Aspergillus, Cladosporium, and Penicillium were reported as dominant in the offices. The RIFE of Yeast, Aspergillus, and Penicillium were 1.26, 1.21, and 1.02, respectively, and it would confirm a higher indoor exposure risk relative to that of outdoors. The RIFE of the common outdoor fungi Cladosporium was 0.48. This study presents a useful index for IAQ assessment regarding relative risk exposure of airborne fungi in A/C offices.

In-cabin Exposure Levels of Carbon Monoxide, Carbon Dioxide and Airborne Particulate Matter in Air-Conditioned Buses of Hong Kong

Bus cabin air quality has not been incessantly monitored in Hong Kong. This study investigates the in-cabin exposure levels of CO, CO2 and PM10 for running buses in Hong Kong that are equipped with Euro II, III and IV engines. A representative urban—suburban bus route was chosen and there were no significantly different in-cabin CO levels reported among engine types and between rush and non-rush hours. However, in-cabin CO level was found significantly associated with ambient/roadside CO level; the former was altogether higher than the latter due to the bus’ own exhaust. Regarding in-cabin PM10 concentration, the engine type played a major role. The outcome demonstrates that new buses (i.e. Euro IV) generally provide a better in-cabin environment for commuters. Therefore, implementation of an air filtration upgrade, together with a routine filter cleaning schedule, is an effective measure to ameliorate bus cabin air quality. This study also provides useful information for further investigation into the causal relationship between health risks and long-term air pollution exposure in local bus cabins.

An Experimental and Numerical Study on Deposition of Bioaerosols in a Scaled Chamber

This work presents an experimental facility designed and built with the objective of understanding the deposition of bioaerosols in indoor environments. Multiple depositions of two microorganisms Staphylococcus and Micrococcus inside a test chamber were investigated under two air mixing conditions. Airflow rate was demonstrated to have an influence on the concentration homogeneity. An increased proportion of particle deposition was found in the floor section near the chamber wall opposite to the air inlet when air mixing was not enhanced by the mixing fans. Both the experimental results and Eulerian-Lagrangian computations revealed that a small mixing fan inside the chamber prompted very effective mixing while non-homogeneity was observed even at a very high ventilation rate. The results showed that both ventilation rate and mixing conditions in the ventilated chamber have influence on the bioaerosol dispersion and deposition.

Fungi - An indoor air quality assessment parameter for air-conditioned offices

Representative assessment parameters are proposed for indoor air quality (IAQ) audit in various strategies and guidelines.1 In Hong Kong, assessment of indoor airborne fungi is not incorporated in many IAQ audits of air-conditioned offices, although the exposure to airborne fungi could cause a variety of adverse health effects. An IAQ assessment for a local office will audit 12 parameters, including air temperature, relative humidity, air velocity, carbon dioxide, carbon monoxide, respirable suspended particulates, nitrogen dioxide, ozone, formaldehyde, total volatile organic compounds, radon, and airborne bacteria. This paper reviews recent studies of the indoor airborne fungi levels and IAQ assessments in some air-conditioned offices of Hong Kong and evaluates the contribution of the airborne fungi to an unsatisfactory IAQ in the environment. The unsatisfactory rates regarding the assessment parameters were evaluated using the Monte Carlo simulations with measured data in Hong Kong Offices. In particular, the impact of selecting representative IAQ assessment parameters was examined against an express assessment protocol (EAP), which assessed some dominant contributors of unsatisfactory IAQ.2 The results reported that the three top ranked contributors for unsatisfactory IAQ were total volatile organic compounds (TVOC), indoor airborne fungi count (AFC) and airborne bacteria count (ABC) for air-conditioned offices of Hong Kong. Practical applications: This study has shown that the assessments of airborne fungi levels in office environment is an important issue and further investigations for the airborne fungi in the IAQ audits were thus recommended. The results of this study could be a useful source of reference for policymakers in evaluation of an effective IAQ assessment protocol with some representative IAQ assessment parameters.

Air quality influence on chronic obstructive pulmonary disease (COPD) patients’ quality of life

UNLABELLED Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death. The relationship between urban air pollution and its short-term health effects on patients suffering from COPD is confirmed. However, information about the impact of air pollutants upon the quality of life (QOL) in patients with COPD is lacking. Through a cross-sectional survey, this study investigates such impact in terms of the scores of the (Chinese) chronic respiratory questionnaire (CCRQ) and the measurements of indoor air quality (IAQ), lung function and Mosers activities of daily living (ADL). Using Yules Q statistic with a cutoff |Q|>0.7 to identify the strong relationships between environmental parameters and CRQ sub-scores, this study reveals that patient emotion is strongly associated with indoor environmental quality although the evidence of a causal relationship between them needs further research. PRACTICAL IMPLICATIONS As QOL in patients with COPD and indoor environmental parameters are strongly associated, indoor air pollutants must be monitored for related studies in the future.

Bayesian Assessments for Acceptable Airborne Bacteria Levels in Air-Conditioned Spaces:

The level of indoor airborne bacteria is usually selected as a reference to identify the cleanliness of a Heating, Ventilating and Air-Conditioning system. This study proposes an epistemic approach for assessing acceptance of air-conditioned spaces against certain acceptable airborne bacteria levels. From the thermal environmental conditions and a sample test of the airborne bacteria level, the assessment model can give a rapid estimation of the probability of an unsatisfactory indoor environment. An office having a higher risk of unsatisfactory Indoor Air Quality (IAQ) would require a lower sample test value to fulfill the IAQ acceptance at certain confidence level. The model parameters were determined from databases of 529 air-conditioned spaces in Hong Kong, with airborne bacteria levels ranging from 41 to 2304 CFU · m-3, air temperatures from 13.4 to 27.8°C and relative humidities from 29 to 88%. This model would be useful to policymakers for making a fast response to the microbiological pollutant problem while avoiding an inappropriate level of reliance on the results.

Formaldehyde exposure risk in air-conditioned offices of Hong Kong

Formaldehyde (HCHO) is a carcinogenic toxicant commonly present in an air-conditioned office environment. This study examines the lifetime exposure risk of HCHO in air-conditioned offices of Hong Kong under various indoor environmental conditions. Using the regional indoor air quality assessment results of 511 Hong Kong offices recorded from 1996 to 2005, together with the mathematical correlations among HCHO exposure concentration, ventilation and thermal environment verified at 43 other local air-conditioned offices, the exposure risk in terms of loss of life expectancy (USEPA standard) was predicted for an office environment preset at certain air temperature and atmospheric carbon dioxide (CO 2) level. It was reported that the average increment of HCHO exposure risk was 2% for every 1°C increment in the air temperature range of 22.5—25.5°C, or 2.5% for every 10 ppm increment in the CO2 concentration range of 800—1000 ppm. This study presents useful information on HCHO exposure risk evaluation for air-conditioned offices associated with various policies on indoor air temperature and ventilation demands. Practical applications: This study outlines an approach to lifetime exposure risk assessment for HCHO inhaled in air-conditioned offices of Hong Kong under various indoor environmental conditions. In a typical office environment, the findings demonstrated that the average increment of HCHO exposure risk was 2% for every 1°C increment in air temperature or 2.5% for every 10 ppm increment in CO 2 concentration.

An implementation choice of assessment parameters for indoor air quality (IAQ) in air‐conditioned offices

Purpose – The purpose of this paper is to propose a screening test for indoor air quality (IAQ) assessment by auditing only a few “dominant” contributors for preliminary measurements in air‐conditioned offices.Design/methodology/approach – In Hong Kong, up to ten common indoor air pollutants have to be audited in determining the IAQ acceptance for typical air‐conditioned offices. Indeed, parameters could not be uniformly contributed to the assessed “IAQ satisfaction”. The study reviews the past ten‐year assessment experiences in Hong Kong and investigates the “dominant” contributors of unsatisfactory IAQ for screening tests.Findings – When compared with the “full” assessment of all ten listed parameters, a screening test with assessment parameters reduced by half would correctly identify 96 per cent unsatisfactory and 95 per cent satisfactory cases.Research limitations/implications – The screening test was developed with the reported patterns of the ten common air pollutants from on‐site measurements and ...

Residential Lifetime Exposure Risk of Formaldehyde in Residential Buildings in Hong Kong

Abstract Formaldehyde (HCHO) is a carcinogenic toxicant commonly presented in indoor air and can impose long-term health hazards to building occupants. In this study, the exposure risk of HCHO in residential homes of Hong Kong was evaluated in terms of the expected loss of life expectancy (LLE). In particular, home staying time distribution patterns generated from reported home activity patterns using Monte-Carlo simulations were used to evaluate the cumulative exposure for residence at an age up to 70. With regional assessment results of HCHO levels in over 700 residential homes of Hong Kong from 1995 to 2002, mathematical expressions of the HCHO exposure risk were proposed. The results showed that for a resident, age 70, the estimated risk of LLE at 95% confidence intervals was 0.3 day to 10.4 days due to the exposure of HCHO in the home. This study would be a useful reference in evaluating the environmental risk of HCHO in residential homes of Hong Kong.