As you may recall from prior posts, the warning threshold for a "reproductive toxicant" under Proposition 65 is determined by finding a "no-effects" level, and then dividing that number by 1,000.
The Office of Environmental Health Hazard Assessment (OEHHA), a part of Cal-EPA, administers much of the Prop. 65 regulatory apparatus. OEHHA recently gave notice that it is considering listing hydrogen cyanide and cyanide salts as a male reproductive toxicant because of an IRIS determination of a male reproductive endpoint (based on animal studies) and the classification of these "chemicals" (a Prop. 65 term-of-art) by EPA. http://www.oehha.ca.gov/prop65/CRNR_notices/admin_listing/requests_info/pdf_zip/Cyanide051311.pdf Under Prop. 65, a chemical can be listed based on a determination by an authoritative body utilizing scientifically valid data.
At this point in the administrative process, OEHHA is still in the information-gathering phase of the assessment. See the link above for how to provide comments.
In anticipation of industries and circumstances in which, if listed, a warning might have to be given, OEHHA notes that these chemicals are used in mining, metallurgy, manufacturing, photography, electroplating, and as a rodenticide; they are also released from biomass burning, volcanoes, and natural processes. And, of course, OEHHA notes that these chemicals are a component of tobacco smoke.