Permatex #2 with a plain gasket applyed to intake side and housing side will never leak. The permatex is a googy paste.
Proposition 65 requires California to publish a list of chemicals known to cause cancer, birth defects or other reproductive harm. This list, which must be updated at least once a year, has grown to include approximately 900 chemicals since it was first published in 1987. This is a good guess!
Permatex #1 and 2, are the only sealers, I use. Haven't let me down, in 50+ years.