The following is/are a rich source of fluoride:
The dried tea leaves contain 100-400 ppm fluoride, depending on the brand.
Fish products, in particular canned fish such as salmon and sardines have a fluoride content of up to 20-40 mg/kg. The meat of fish is relatively low in fluoride content (2-5 mg/kg) as compared with fish protein concentrates, which may contain up to 370 mg/kg.
Certain plants, such as taro, yams, and cassava, cabbage have been found to contain relatively high fluoride levels.
Essentials of preventive and community dentistry
Soben Peter
5th edition
page no. 243
Dried fish
Tea leaves
Cabbages
All of the above