Chlorine – can react with other organic substances in the environment and generate hazardous compounds such as furans and dioxins
Formaldehyde (used mainly in chemical toilets for camping) – is carcinogenic and shown to cause mutations in animals
Diethylene glycol monobutyl ether – volatile organic compounds harmful to aquatic organisms
Sodium dichloroisocyanurate – very toxic to aquatic organisms – may cause long-term damage in the environment
Chlorinated phenols – respiratory and circulatory toxins
Triclosan – a cumulative toxin, primarily used for anti-bacterial purposes, but can also damage plant, animal and aquatic life.
According to an article on Toiletable.com, many of the de-scaling ingredients used in toilet cleaners are based on petrochemicals, i.e. crude oil. Often these chemicals are not removed water treatment facilities.
Treehugger’s Best of Green Awards recognized Biokleen for Best Cleaning Products. Start there for healthy cleaning ideas.
Also, this article is very helpful: Cleaning toilets the environmentally friendly way