Dioxin emissions from a Kwai Tsing incineration facility are safely below international standards, a report has found.

Kwai Tsing district councillors were briefed today on an independent expert's report on incineration of dioxin-containing residues at the Chemical Waste Treatment Centre on Tsing Yi between January 5 and 9.

According to Professor Jonathan Wong's report, analysis of samples taken on January 6 and 8 revealed the concentration of dioxin in stack emissions was 0.0004 ng/cubic metre on average, well below the prevailing international standard for incinerator dioxin emissions of 0.1 ng/cubic metre.

The concentration of dioxin in kiln-bottom ash was 1.53 ng/kg on average, far below the most commonly acceptable soil contamination criteria of 1,000 ng/kg.

Incineration safe

Given the very low concentration of dioxins during the period, Professor Wong said the incineration process is effective and environmentally safe in destroying dioxin-containing residues.

The monitoring results on average ambient dioxin concentration at five locations in Kwai Tsing ranged from 0.090 to 0.126 pg/m3, higher than the baseline monitoring results which were in the range of 0.010 and 0.100 pg/m3 obtained between November 2003 and October last year.

However, the result fell within the range of dioxin level of 0.035 and 0.345 pg/m3 recorded by the Environmental Protection Department in Tsing Yi, Central and Tsuen Wan during the past five years.

Winter increase

Professor Wong said the relatively higher dioxin level in ambient air was very likely due to the periodical increase in pollution levels in winter months, adding the emission during the incineration process was not the cause.

The Civil Engineering & Development Department agreed with Professor Wong's recommendation that with the implementation of the stringent monitoring measures as being adopted in previous incinerations, it would be safe for the centre to proceed with the next incineration.

The department will continue to maintain high transparency in the remaining transportation and incineration operations and will update the Kwai Tsing District Council on the progress.