A review into the New South Wales Environment Protection Authority's (EPA) management of significantly contaminated sites found the agency routinely did not declare contaminated sites where property values could be affected.

The Chief Executive Officer of the EPA, Barry Buffier, said human health remains the agency's main consideration in reporting contaminated sites to the community.

"If the land was significantly contaminated and posed the risk to human health or the environment we would declare it as significantly contaminated regardless of any impact on property value," he said.

The review, written by Professor Mark Taylor and Isabella Cosenza, found the internal guidelines state that declaring land, particularly residential land, can affect the valuation of a property and the EPA does not declare off-site residential land to avoid unnecessarily blighting the land.

But Mr Buffier admitted the guidelines were confusing.

"It's a little bit ambiguous and we are looking at our guidelines now just to make sure it's absolutely clear," he said.

Opposition environment spokeswoman Penny Sharpe said the EPA's guidelines suggest important information is not being published.

"It's clear from the review that there are internal guidelines working to hide information from the public on the basis that the EPA for some reason has decided it wants to be concerned about property prices," she said.

Ms Sharpe has called on the Government to address the issue.

"It is not the EPA's job to be worrying about house prices. It's the EPA's job to be watching over contaminated lands, informing the public, making sure it's remediated and monitoring ongoing contamination."

She also said transparency for home buyers and investors is necessary.

"Families rely on the information that's available when they're purchasing property and they need to know if their kids are playing in the backyard or they're planting fruit and vegetables that they're not planting that into contaminated land," she said.