DANGEROUS levels of arsenic, lead and mercury have been discovered on a nature strip between the chemical company Orica's Port Botany plant and a large residential area, contradicting claims there is no evidence of off-site contamination or health risks.

In response to Fairfax Media's investigations, the Environment Protection Authority has announced it will conduct an independent review of all information about historical mercury emissions at Botany. A spokeswoman for the EPA said it would involve a thorough analysis of available data to determine if further information was needed to assess residual health risk to the public.

Dangerous substances ... Len Mahony outside the Orica chemical plant. Credit:Mick Tsikas

The review, to be made in consultation with NSW Health, will be paid for by Orica. The company will not have a role in the selection of experts or in developing terms of reference; these will be decided by the EPA.

The results taken from a topsoil sample and analysed by Andrew Helps, a mercury recovery expert, revealed high levels of the three top-ranked toxic metals in the world as well as seven other highly ranked toxic metals.