The information below as to fluoride based pesticides is thought provoking; does anyone know if this is still an issue?
To put things into context a UK dietary survey http://www.food.gov.uk/science/resea...s#.UmuWAlOt_os found the highest fluorine levels were in the fish food group 1.9mg per Kg or 1.9 parts per million (Sorry got that wrong earlier 
). Fish is generally regarded as a healthy food and a good source of iodine, which brings us back to the question is iodine deficiency rather than fluoride intake the primary issue (except in very young infants, because it seems breast milk production filters out most fluoride, and what are the implications of that).
(Perchlorate as a blocker may be a particular case as it is reported to be taken up better than iodine, which would explain why it appears to preferentially block iodine uptake; so upping iodine intake may help but not fully negate the effects of perchclorate)
This East African paper http://eurekamag.com/research/003/14...-in-africa.php (PDF can be downloaded free) confirms fish, both fresh and marine, contain significant amounts of fluoride and particularity in the skin, as apparently do some food stuffs there (Is that due to high levels of flouride in soils or water, and what implications does that have for the west; are we increasing soil levels through for example the use of coal, and or using treated water for husbandry or crop irrigation).
This paper looks at more northerly species. http://www.google.com/url?sa=t&rct=j...55123115,d.Yms Fluoride in the fillets is generally modest but again high is skin and bones. So sardines are likely to be a significant source of fluoride. Coastal populations in some countries such as Portugal ate sardines regularly. This paper looking at goiter in Europe says that it was rare in coastal Portuguese populations, http://www.google.com/url?sa=t&rct=j...55123115,d.Yms which brings us back to iodine, as well maybe as the importance of other marine nutrients including selenium and other minerals - we are back to complex interactions again !
Goiter is common in areas of East Africa, as apparently is fluorosis of the teeth; is this due to iodine deficiency or a high fluoride intake - most likely iodine deficiency I postulate.
The paper reports oyster tissue contained in the order of 240mg of fluorine per Kg! ( I am trying to check this figure as it seems very high - but the general precept still holds as it appears fish are in comparative terms high in fluoride, but also a source of iodine; figures on iodine levels in foods are not easy to find either !) I have not seen goitre or fluorosis being reported as a consequence of regular oyster consumption, or being Inuit, which again brings us back to the question is iodine deficiency the main issue. (Marine food contain iodine, but apart from milk most land based foods contain little iodine)
This report ( I will add the reference tomorrow as I have lost the link) would seem to suggest that western sources of higher levels of fluoride include (or maybe used to?) common foods such as grape juice and cereals, which self evidently are unlikely to contain significant iodine.
Some suggest that in considering whether to fluoridate water we should be mindful of the high levels of fluoride in food. The question also occurs to me how do dental trials looking at fluoride differentiate the effects of fluoride in water and larger ? amounts in food ?
The site below raises the issue of the use of pesticides that contain fluorine. I do not know if they are still in use.
Fluoride residue tolerances approved for food by US EPA as of July 15, 2005.
http://www.fluoridealert.org/wp-cont...july.2005.html
http://fluoridedetective.com/fluorid...uryl-fluoride/
Sulfuryl Fluoride:
Fluoride Fumigated FoodSulfuryl fluoride is a pesticide used to fumigate food warehouses. Kills bugs and rodents dead. Toxic?
Oh heck yeah!!
The EPA classifies it in the most acutely toxic category of pesticides: a restricted use pesticide (1) which means that food products and packaging must be removed from warehouses before they can be fumigated. No food contact allowed. Makes sense, right?
Well all this changed in 2004. Since 2004 sulfuryl fluoride has become widely used ON foods. (I bet Dow Chemical lobbyists earned a fat bonus on this.)
Now EPA allows these fumigations to create fluoride residues of up to 70 ppm fluoride “in or on” all processed foods (except specified foods) and 130 ppm “in or on” wheat!
Fluoride Alert has compiled a list of tolerated fluoride levels in fumigated foods. (5)(6)(7)(8)
Labeling of exposed foods
AND, if that’s not bad enough, no regulations require exposed foods to be labeled accordingly! Consumers have no warning whether a food has been fumigated with sulfuryl fluoride. And since fluoride is flavorless, odorless, and colorless, we are intentionally left totally in the dark on the nature of what we’re eating.
How much is 70 ppm fluoride anyway?
Look at it this way: In January 2011 the CDC lowered the amount of fluoride to be in our drinking water from 1.2 ppm to 0.7 ppm due to health concerns. With that in mind, consider your fresh or frozen dinner vegetables laden with up to 70 ppm of fluoride or the flour in your bread having 130 ppm fluoride. Ouch!!