EXECUTIVE SUMMARY

Questionnaire Survey

The questionnaire survey found that some 32% of the respondents were dissatisfied with the IAQ of their workplace. This figure is comparable to that reported in similar studies by the World Health Organisation (WHO).

Detailed Field Measurements

In the field measurement survey, carbon dioxide was the pollutant most often violated the international standards on IAQ: in the summer survey, 37.5% of offices had, over an 8-hour period, a mean carbon dioxide level exceeding 1,000 ppm. These excessively high levels of carbon dioxide were found to be caused by the high occupancy density in Hong Kong and inadequate ventilation. Indeed the fresh air content provided by the air-conditioning systems in 90% of the office buildings was found to be insufficient and well below the minimum requirement of 7.5 litres per second per occupant specified by the revised ASHRAE Standard 62-1989R of the American Standard for Heating, Refrigeration and Air-conditioning Engineering.

As a result of inadequate ventilation, the bacteria count in terms of "colony forming units per cubic meter" (cfu/m3) was higher than the recommended level of 1,000 cfu/m3 in 20% of the offices included in the summer survey. Fungal levels exceeded the recommended level (500 cfu/m3) less often but toxigenic species such as Aspergillus versicolour and Penicillium aurantiogriseum were found in over 10% of the premises. The dust collected in these premises all contained quantities of glucan and endotoxin (which cause inflammation and come from fungi and bacteria respectively) as well as dust mite allergens. These are thought to contribute to the allergic reactions experienced by many people in indoor environments.

Formaldehyde levels were also found to be above the WHO guideline of 100 ug/m3 in 32.5% of the offices in the summer survey. Formaldehyde emissions were associated mainly with chipboard, plywood using urea formaldehyde as an adhesive, and some coating polymers used to treat the surface of upholstery. Apart from formaldehyde, other volatile organic compounds were found in levels below the WHO guidelines or less than 5% of the threshold limit values (time-weighted average) used in industrial workplaces.

There were four premises where the levels of organic compounds, such as toluene, xylene (o-, m- and p-) and benzene, were exceptionally high. This was found to be due to the use of thinner in painting and woodwork during the redecoration of offices on the same floor as the offices where the sampling was taking place. This shows the importance of monitoring and controlling activities which may affect other occupants sharing the same floor and/or the same ventilation system.

Statistical Analysis

In the statistical analysis, the results showed significant correlation between the occupants' perceptions and measured parameters of IAQ including temperature, humidity, air change per hour, and levels of carbon dioxide, carbon tetrachloride, dichlorobenzene, bacteria and fungal counts. There was also a positive correlation between occupants' perceptions and 21 medical symptoms. For other parameters such as formaldehyde, toluene, xylene (o-, m- and p-) and trichloroethylene, the correlation, although significant, showed a reverse trend. These findings suggest that, while occupants are aware of environmental conditions such as the level of carbon dioxide and temperature, their sensitivity to important pollutants such as formaldehyde and organic solvents associated with thinners (decoration work), may be overshadowed by the "feel good" factor associated with newly decorated premises. This shows the importance of conducting both questionnaire surveys of occupants and sophisticated analytical tests of volatile organic compounds and formaldehyde: the former, to obtain a good indication of the general indoor environment, and the latter to ensure a thorough investigation of IAQ.

There was no significant correlation between levels of pollutant in indoor air with outdoor air except for respirable suspended particulates, with indoor air at a lower level as dust was trapped by filters in the ventilation system. Pollutants which showed higher levels indoor from outdoor had indoor emission sources, such as carbon dioxide, carbon monoxide, formaldehyde, volatile organic compounds, radon as well as bacteria and fungal counts. This demonstrates the importance of controlling the indoor air quality which can effectively reduce exposure of occupants in an indoor environment.

By carrying out a detailed survey of 40 carefully selected representative office sites and the 2,000 questionnaire surveys covering at least 800 identifiable buildings, it was possible to make a projection of the likely indoor air quality of the entire office building stock in Hong Kong within reasonable statistical confidence. The evidence of levels of indoor air pollution above international standards in many of the offices studied demonstrates the need for public guidance on how to manage the indoor air quality in these premises and recommended standards. A summary of the levels of indoor air pollutants found in the office buildings studied is provided in Table 1.

IAQ in Public Places

The pilot study of IAQ in public places found specific problems such as failure to comply with existing regulations or presence of pollutants at levels which violated internationally accepted guidelines. Table 2 provides a summary of the findings for public places.

For restaurants in general, the current smoking control measure is insufficient and efforts should be made to require segregation of ventilation systems to effectively control the entrainment of tobacco smoke to no-smoking areas. Adhering to a set of code of practice designed for this purpose or administrative requirements on smoking policy would yield positive improvement to the air quality indoor in such premises. For restaurants with naked fire in the dining area, the local exhaust provisions should be required to achieve IAQ objectives of nitrogen dioxide and carbon monoxide.

The results of the survey of the Mass Transit Railway (MTR) showed that IAQ at the MTR concourses and platforms during normal operational conditions was comparable even with the health/comfort-based IAQ objectives recommended in this Study for non-industrial and public places. The concentration of carbon dioxide inside train compartments during peak-hour period was high due to extremely crowded conditions, but it was still within the guideline for subway design in the USA.

Study on the Practice of Other Countries

The study showed that other countries are devoting resources to establishing standards, providing mitigation measures, and public education initiatives with the aim of improving indoor air quality. Of the advanced Asian countries, Japan has already introduced an indoor air quality control and monitoring requirement under the Ordinance of Office Sanitation, Singapore issued the Indoor Air Quality Guideline in 1996, and South Korea has an Indoor Air Quality Management Ordinance in the pipeline. In the west, the USA took the lead in proposing an Indoor Air Quality Bill under the Occupational Safety and Health Administration (OSHA) in 1993 but has so far failed to secure political agreement to the Bill. In the UK the issue also suffers from lack of support from political leaders. The Nordic countries, however, have been more active with Sweden and Finland adopting stringent codes to control IAQ under their respective ventilation laws.

In all these countries, there are already many regulations which in some way affect indoor air quality. That is also the situation in Hong Kong. Table 3 gives a list of existing responsibilities of government departments that are relevant to IAQ.