During this litigation about whether Prop. 65 requires warnings about the carcinogen acrylamide in coffee, the Office of Environmental Health Hazard Assessment issued a legislative regulation stating that chemicals known to be included in coffee created by the process of roasting or brewing coffee do not pose a significant risk of cancer. (27 CCR 25704.) The trial court correctly granted the defendant coffee companies summary judgment based on the regulation. Assuming that an agency must explain a departure from prior conclusions, no explanation was needed here because an earlier study merely concluded that levels of acrylamide in coffee exceeded the safe harbor level, not that there was enough acrylamide in coffee to cause cancer. The agency substantially complied with its obligation to explain why it did not change its regulation based on plaintiff’s comment on the proposed regulation by addressing the substance of plaintiff’s concern even if not mentioning that plaintiff had raised it. The regulation was supported by scientific evidence and was not arbitrary or capricious.