Cal. Labor Code § 6390

The manufacturer of any hazardous substance listed pursuant to the provisions of Section 6380 shall prepare and provide its direct purchasers of the hazardous substance with an MSDS containing the information specified in Section 6391 which, to the best of the manufacturer’s knowledge, is current, accurate, and complete, based on information then reasonably available to the manufacturer. For purposes of this section, a substance, mixture, or product shall not be considered a hazardous substance if present in a physical state, volume, or concentration for which there is no valid and substantial evidence that any adverse acute or chronic risk to human health may occur from exposure. The manufacturer shall revise an MSDS on a timely basis as appropriate to the importance of any new information which would affect the contents of the existing MSDS, and in any event within one year of such information becoming available to the manufacturer. If the new information indicates significantly increased risks to, or measures necessary to protect, employee health, as compared to those stated on the MSDS previously provided, the manufacturer shall provide such new information to persons who have purchased the product directly from the manufacturer within the last year.