State Regulatory Support:
Proposition 65 - Safe Harbor Levels

California’s Office of Environmental Health Hazard Assessment (OEHHA) establishes threshold levels, often called “Safe Harbor Levels,” which trigger warning and discharge prohibition requirements under

Proposition 65

. OEHHA has published default Safe Harbor Levels for many

listed chemicals

, but others lack default values, even many years after the compounds have been added to the list.

A potable water source containing chemicals that fall beneath OEHHA’s Safe Harbor Levels for warning labelsCompanies are required to provide “clear and reasonable warnings” and terminate discharges one year after a chemical is listed under Proposition 65 if exposures exceed the Safe Harbor Level. If OEHHA has not published a default Safe Harbor Level, companies must establish their own Safe Harbor Level as described in regulations.

TSG’s scientists have the toxicology expertise required to independently establish Safe Harbor Levels (NSRL and MADL) that companies can use with confidence in risk assessments until defaults are published by OEHHA.

Safe Harbor Levels are described as follows:

▲ Carcinogen Safe Harbor Levels are termed No Significant Risk Levels (NSRL). They are
based on the most sensitive study meeting certain requirements and calculations
described in regulations for an exposure level that results in 1 excess cancer in an
exposed human population of 100,000.

▲ Reproductive Toxin Safe Harbor Levels are termed Maximum Allowable Dose Level
(MADL). They are based on the most sensitive study meeting certain requirements at a
level that is 1,000 fold below the no observable effect level (NOEL) of the study.

TSG’s consultants are experienced at calculating NSRL and MADL using regulations and underlying documentation. Companies have used TSG's independent NSRL and MADL to comply with Proposition 65 until default values are published by OEHHA. TSG's values and documentation, along with appropriate risk assessments, establish a record of Proposition 65 compliance that deters


 under the Act.
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