Modern incineration the best method to tackle clinical waste

The Government shares community concerns about the potential risks from dioxin and other heavy metals, Principal Assistant Secretary for Planning, Environment and Lands, Mr Steve Barclay said today (Tuesday).

After careful consideration the Government is convinced that incineration, adopting the most stringent emission controls and segregation of potentially harmful materials, is the best way forward, he said.

"The Government fully supports public proposals on waste separation, reduction and reuse as the key strategies in clinical waste management. These are already being done."

However, some of the proposals containing criticisms of incineration are either not applicable to the local situation or are inaccurate, he said.

The incinerator in the Chemical Waste Treatment Centre (CWTC) can handle all types of clinical wastes, and is capable of controlling the emissions well within the most stringent international standards.

The rotary kiln and the combustion chamber of the incinerator of CWTC can operate up to 1,200 degrees Celsius at which temperature all hazardous chemicals such as dioxins are destroyed. The design of the incinerator has also catered for the prevention of reformation of dioxins.

Most wastes from hospitals and clinics that contain Polyvinylchloride (PVC) such as baby diapers with plastic linings are separated and disposed of as municipal solid waste. They will not be incinerated at the CWTC.

"PVC is the type of plastic that creates dioxin when incinerated. Other plastics do not produce dioxin," Mr Barclay said.

Hospitals under the Hospital Authority already separate mercury waste from clinical waste. This is recycled, not incinerated or dumped in landfills.

Besides, he said, medical instruments containing mercury are gradually being replaced by electronic devices.

"The environmental risks in using large-scale autoclaving, microwave systems and chemical disinfection equipment for treating clinical waste are not well documented.

"Such treatment methods may emit unknown volatile organic compounds which can be equally hazardous."

Autoclaves, microwave systems and chemical disinfection equipment cannot remove the toxicity or destroy the residual amount of cytotoxic drugs, pharmaceuticals and other chemicals in the syringes and on sharp instruments such as scalpels. They are not appropriate for dealing with human body parts.

The operating temperature of autoclaving and microwave clinical waste are normally 131 and 95 to 100 degrees Celsius respectively, which is much lower than that of incineration. Their effectiveness in destroying pathogens is much lower.

The cost of a centralised autoclave would be roughly the same as the CWTC modification option. The costs quoted by a concern group to the Government have not included the costs of land, emission controls, installation and other associated waste management facilities.

"The risks associated with incineration of clinical waste at the CWTC have been exaggerated. The emissions of dioxin could be increased by 100,000 times and still comply with World Health Organisation (WHO) recommendations," Mr Barclay said.

Statistically, the risks per million per year can be compared with other possibilities:

CWTC 0.000057

Road Accidents 100

Working in Construction 92

Working in Manufacturing 23

Being hit by lightning 0.1

"In conclusion, incineration at the CWTC is safe, environmentally sound, and cost-effective.

"Other alternative disposal methods could complement, but not replace incineration," he said.

End/Tuesday, December 14, 1999