I’ve been wearing Mephisto sandals almost every day for I don’t know how long. At least 15 years. I just buy the same Helen sandals over and over. They are the only shoes I can walk any distance in and never have my feet hurt or get tired. Finally I found some information about the materials. They are handcrafted in France and Portugal. The leathers are highest quality and have “natural tanning.” The soles are natural rubber obtained from latex. I’ve never had any problems of toxic exposure from any pair of Mephitis shoes I’ve purchased.