There is an article by Amanda Ruggeri at BBC on February 12, 2025 titled Natural doesn’t always mean better: How to spot if someone is trying to convince you with an ‘appeal to nature’. It also was discussed by Steven Novella at Science-Based Medicine on that day in another article titled BBC Takes On Appeal to Nature Fallacy. And there is a Wikipedia page on Appeal to nature.
Natural may be terrible. For example, poisonous arsenic can be in well water. There is a web page at the Minnesota Department of Health titled Private Well Protection Arsenic Study with the following information:
“Approximately 10 percent of new wells in Minnesota contain arsenic above the drinking water standard. Drinking water with low levels of arsenic over a long time increases the risk of diabetes and increased risk of cancers of the bladder, lungs, liver, and other organs. It can also contribute to cardiovascular and respiratory disease, reduced intelligence in children, and skin problems such as lesions, discolorations, and the development of corns. Health impacts of arsenic may not occur right away and can develop after many years, especially if you are in contact with arsenic at a low level over a long time.
Arsenic can be found in groundwater throughout Minnesota, but is more likely in some areas than others, due to the way glaciers moved across Minnesota. Because it has no taste and no odor, testing is the only way to know whether or not a well has arsenic in it. All new wells must be tested for arsenic before being placed in service.”
Arsenic can also show up in foods grown in water like rice. In November 2014 there was a Consumer Reports article titled How much arsenic is in your rice? and a long report titled Analysis of Arsenic in Rice and Other Grains. In July 2023 there is an article by Lihchyun Joseph Su, Tung-Chin Chiang, and Sarah N O’Connor at Frontiers in Nutrition titled Arsenic in brown rice: do the benefits outweigh the risks?
How about poisonous plants, for which Wikipedia has a web page. And the Wikipedia page about Cassava discusses how there is cyanide in bitter cassava (manihot esculenta).
What about fish? There is a Wikipedia page about poisonous fish. The Wikipedia page on the Fugu (pufferfish) says it can be deadly if not properly prepared, as shown in a YouTube video from The Simpsons.
The adapted water warning sign and Poison Garden gates are from Wikimedia Commons.