请看第4个视频中2:27-2:40的图：美国自来水里氟化物的含量是健康含量的近300倍

下面是ADA的公告：

http://www.ada.org/sections/advocacy/pdfs/fluoride_report_response.pdf

看上文的最后一段：

...insure children do not ingest too much fluoride. The good news is that parents and other caregivers can monitor the use of all fluoride-containing products by children younger than 6 years by placing only a pea-sized amount of fluoride toothpaste on a young child’s toothbrush at each brushing. Young children should be supervised while brushing or using a mouthrinse so they learn to spit, and not to swallow. Before the age of two, children should not be allowed to use a fluoride toothpaste for brushing.

这里有更加有意思的公告：

http://ebd.ada.org/contentdocs/ADA_Evidence-based_Infant_Formula_Chairside_Guide.pdf

简单点说吧：美国的自来水里氟化物的含量不是太低了，而是太高了，特别是对幼儿。