This bill prohibits an agency from disseminating, proposing, or finalizing any regulatory action by promulgating rules or a similar action for a substance, mixture, or chemical related to drinking water, water pollution control, hazardous substances, contaminated site remediation, air quality, or solid or hazardous waste handling unless the following criteria is met:  All scientific and technical information relied on to support the regulatory action is based upon the best available science.  With respect to human health, the best available science indicates that exposure to the substance, mixture, or chemical that exceeds the level proposed in the regulatory action is causally linked to manifest bodily harm in humans. However, this bill only applies to agency regulatory actions that are adopted on or after July 1, 2025, and that are more stringent than any applicable federal regulatory action or adopted in the absence of a federal regulatory action. Additionally, this bill must not be construed to impact a regulatory action by an agency (i) in existence before July 1, 2025; (ii) in furtherance of federal agency primacy requirements; or (iii) that is the substantive equivalent to a federal regulation. As used in the provisions above, "best available science" means science that (i) is reliable, unbiased, and reasonably applied to the agency's regulatory action; (ii) maximizes the quality, objectivity, and integrity of information; human, animal, and other relevant scientific studies; and human health risk-based assessments; and (iii) involves the use of supporting studies that are conducted in accordance with sound and objective scientific practices utilizing data collected by generally accepted methods or best available methods, subject to independent verification, and published in a refereed journal. Such a journal must (i) use an editorial board or critical review panel of subject matter experts in the relevant scientific or technical disciplines who critically and objectively assess the methodology and analysis of submitted scientific studies in a nonpartisan fashion and provide editorial services prior to publication, (ii) take meaningful steps to avoid biases in its scientific review process, and (iii) not charge publication or submission fees to authors. ON APRIL 3, 2025, THE SENATE ADOPTED AMENDMENT #1 AND PASSED SENATE BILL 880, AS AMENDED. AMENDMENT #1 rewrites this bill to generally prohibit a governmental agency from adopting a rule or establishing numeric criteria or numeric limitations applicable to a contaminant, pollutant, hazardous substance, solid waste, or hazardous waste that relates to drinking water, water pollution control, hazardous substances, contaminated site remediation, air quality, or solid or hazardous waste handling unless: (1) Scientific and technical information relied on to support the rule is based upon the best available science; and (2) With respect to human health, the best available science establishes a direct link, based on generally accepted scientific practice, to manifest bodily harm in humans. In the absence of data from voluntary scientific studies on humans, best available science can be based on tests performed on experimental animal species or human and animal cells that indicate exposure at or above the numeric criteria or numeric limits establishes a direct link, based on generally accepted scientific practice, to manifest bodily harm in humans. This full text of this amendment provides a detailed definition of "best available science." This amendment only applies to agency rules adopted on or after July 1, 2025, that are more stringent than any applicable federal regulation or adopted in the absence of a federal regulation. This amendment does not apply to: (1) Any rule required by federal law; (2) Any rule that is the substantive equivalent to a federal regulation; (3) Any rule of the department of agriculture or the department of health; or (4) Emergency rules.