The state of California maintains an openly available list of chemicals that are known to cause cancer or reproductive harm.
This database is available in CSV format here:
A Wikidata property was created recently by @Gstupp to store the corresponding ids in Wikidata: CA PROP 65 ID (P7524).
These ids could be imported, as well as the known diseases caused by the chemicals.
This would be a good OpenRefine exercise.