ISO 7001

ISO 7001 defines at position 3 to 6 the symbols for toilets.

By the way, this standard includes 168 symbols which are organized in the six categories “public facilities”, “transportation facilities”, “public behaviour”, “commercial facilities”, “tourism, cultural and heritage” and “sporting activities.

Source: https://www.iso.org/obp/ui#iso:grs:7001:PI_PF_003