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Comment by colordrops | Hacker News Reader

Harvard study finding fluoride in water does negatively impact childhood development:

http://www.hsph.harvard.edu/news/features/fluoride-childrens...

It's important to note that this study was performed in China where they don't intentionally fluoridate their water supply. There are many areas with natural (or industrial waste..) levels of fluoride and many of these areas far exceed the level recommended for use in the US.

The current target concentration in the US is 0.7mg/L and is routinely monitored and lowered if the background level is too high where some of the 'hot spots' in China that saw childhood development issues had water containing above 6mg/L and one area had a range from 118mg/kg to 1,361mg/kg (thank you coal mining).

Another confounding factor is that many of the areas with high fluoride levels also had high aluminum, mercury, and arsenic levels as well.

I'd like to see a study comparing IQs or development with actual usage levels and without the heavy metal pollutants from industry.

Full HSPH study:

http://ehp.niehs.nih.gov/wp-content/uploads/2012/09/ehp.1104...

What's your agenda in coming in and claiming the paper is irrelevant? It would have been better to let people read the paper and come to their own conclusions instead of draft off of your biased summary. If you actually read the paper, you would see that some of the regions that reported neurotoxic effects had levels that were lower than the legal limit in the US. Furthermore, the paper claimed that other toxins were factored in to the conclusion. See:

> Drinking water may contain other neurotoxicants, such as arsenic, but exclusion of studies including arsenic and iodine as co-exposures in a sensitivity analysis resulted in a lower estimate, although the difference was not significant.

But this story is already off the front page and you succeeded in burying my post and defending fluoride for some strange reason, so you win.

It should be noted that the negative effects were found in areas with much higher levels of fluoridation (i.e. areas of China with naturally occurring fluoride in groundwater) than are typical in the US. There wasn't enough information to draw conclusions about US fluoridation levels.

The limit for fluoride in US drinking water is 4.0 mg/L, and there are regions in the paper that report cognitive impairment that are much lower than this. You should consider posting analysis or sources for your statements, or just not comment and let the paper speak for itself.

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