(a) Any response action taken or approved pursuant to this chapter shall be based upon, and no less stringent than, all of the following requirements:

(1) The requirements established under federal regulation pursuant to Subpart E of the National Oil and Hazardous Substances Pollution Contingency Plan (40 C.F.R. 300.400 et seq.), as amended.

(2) The regulations established pursuant to Division 7 (commencing with Section 13000) of the Water Code, all applicable water quality control plans adopted pursuant to Section 13170 of the Water Code and Article 3 (commencing with Section 13240) of Chapter 4 of Division 7 of the Water Code, and all applicable state policies for water quality control adopted pursuant to Article 3 (commencing with Section 13140) of Chapter 3 of Division 7 of the Water Code, to the extent that the department or the regional board determines that those regulations, plans, and policies do not require a less stringent level of remediation than the federal regulations specified in paragraph (1) and to the degree that those regulations, plans, and policies do not authorize decisionmaking procedures that may result in less stringent response action requirements than those required by the federal regulations specified in paragraph (1).

(3) Any applicable provisions of this chapter, to the extent those provisions are consistent with the federal regulations specified in paragraph (1) and do not require a less stringent level of remediation than, or decisionmaking procedures that are at variance with, the federal regulations set forth in paragraph (1).

(b) Any health or ecological risk assessment prepared in conjunction with a response action taken or approved pursuant to this chapter shall be based upon Subpart E of the National Oil and Hazardous Substances Pollution Contingency Plan (40 C.F.R. 300.400 et seq.), the policies, guidelines, and practices of the United States Environmental Protection Agency developed pursuant to the federal act, and the most current sound scientific methods, knowledge, and practices of public health and environmental professionals who are experienced practitioners in the fields of epidemiology, risk assessment, environmental contamination, ecological risk, fate and transport analysis, and toxicology. Risk assessment practices shall include the most current sound scientific methods for data evaluation, exposure assessment, toxicity assessment, and risk characterization, documentation of all assumptions, methods, models, and calculations used in the assessment, and any health risk assessment shall include all of the following:

(1) Evaluation of risks posed by acutely toxic hazardous substances based on levels at which no known or anticipated adverse effects on health will occur, with an adequate margin of safety.

(2) Evaluation of risks posed by carcinogens or other hazardous substances that may cause chronic disease based on a level that does not pose any significant risk to health.

(3) Consideration of possible synergistic effects resulting from exposure to, or interaction with, two or more hazardous substances.

(4) Consideration of the effect of hazardous substances upon subgroups that comprise a meaningful portion of the general population, including, but not limited to, infants, children, pregnant women, the elderly, individuals with a history of serious illness, or other subpopulations, that are identifiable as being at greater risk of adverse health effects due to exposure to hazardous substances than the general population.

(5) Consideration of exposure and body burden level that alter physiological function or structure in a manner that may significantly increase the risk of illness and of exposure to hazardous substances in all media, including, but not limited to, exposures in drinking water, food, ambient and indoor air, and soil.

(c) If currently available scientific data are insufficient to determine the level of a hazardous substance at which no known or anticipated adverse effects on health will occur, with an adequate margin of safety, or the level that poses no significant risk to public health, the risk assessment prepared in conjunction with a response action taken or approved pursuant to this chapter shall be based on the level that is protective of public health, with an adequate margin of safety. This level shall be based exclusively on public health considerations, shall, to the extent scientific data are available, take into account the factors set forth in paragraphs (1) to (5), inclusive, of subdivision (b), and shall be based on the most current principles, practices, and methods used by public health professionals who are experienced practitioners in the fields of epidemiology, risk assessment, fate and transport analysis, and toxicology.

(d) The exposure assessment of any risk assessment prepared in conjunction with a response action taken or approved pursuant to this chapter shall include the development of reasonable maximum estimates of exposure for both current land use conditions and reasonably foreseeable future land use conditions at the site.

(e) The exposure assessment of any risk assessment prepared in conjunction with a response action taken or approved pursuant to this chapter shall include the development of reasonable maximum estimates of exposure to volatile organic compounds that may enter structures that are on the site or that are proposed to be constructed on the site and may cause exposure due to accumulation of those volatile organic compounds in the indoor air of those structures.

(Amended by Stats. 2007, Ch. 597, Sec. 1. Effective January 1, 2008.)