Introduction During haze, at what level should Air Pollutant Index (API) showed, public
or private school be closed is not without controversy and is very much
debated. Therefore, the aim of this paper is to objectively quantify the
potential inhaled dose of PM10 associated with exposure at school and home
microenvironments during haze. The result of the health risk assessment will
be used to propose the API level for closing the school during haze episode.
Methods A hypothetical haze exposure scenario was created using the breakpoints of
PM10 concentration for calculation of API and respective inhaled dose during
haze. To determine the potential inhaled dose, we have considered many
factors that include time spent for specific physical intensity at school and
home microenvironments, age-specific and physical intensity-specific
inhalation rate (m3/min), and the indoor/outdoor ratio of PM10. To calculate
risk quotient (RQ), the inhaled dose was compared with the health reference
dose computed based on the concentration of PM10 in the Malaysian
Ambient Air Quality Standard.
Results When considering the specific exposure at each microenvironment (school
and home), the potential inhaled dose of PM10 was substantially lower when
school is closed for both primary and secondary school. The calculated risk
quotient (RQ) indicates that primary school children are likely to be affected
at slightly lower PM10 concentration (equivalent to API of 197) as compared
to secondary school children. Short duration of high physical activity
intensity during school breaks has contributed to a large proportion of inhaled
dose among school children indicating the important to avoid physical
activities during haze.
Conclusion Based on the assessment, taking into account the uncertainty of risk
assessment methodology, we proposed school to be closed when API reach
190 for both primary and secondary schools. These findings and
recommendations are only valid for naturally ventilated school and applicable
in the context of the current API calculation system and the existing
Recommended Air Quality Guideline values in Malaysia.