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Scientists this week urged further research on tungsten— the metal used to make lightbulb filaments, shotgun shells, electrical wires and even wedding bands—to rule out possible health risks to humans and the environment in the wake of studies showing that it may cause reproductive problems in earthworms and stunted growth in sunflowers. 

In an article published this week in Chemical & Engineering News, researchers suggest that not enough is known to determine whether tungsten is safe, and that studies need to be conducted to assess how much is in drinking water and the soil – and whether it poses dangers for humans, animals and plants.

Experts say that tungsten is safe when used in its pure form in lightbulb filaments, jewelry, and electrical devices. But researchers quoted in the article and interviewed by ScientificAmerican.com say that when tungsten gets into the soil (through, say, lightbulbs in landfills), it reacts with substances such as oxygen, forming new chemicals such as polytungstates that may cause growth and reproduction problems in plants and animals. Studies show that sunflowers grown in soil spiked with tungsten powder grow shorter roots, stalks, and leaves and “start looking sickly,” says David Johnson, a toxicologist with the Environmental Laboratory of the U.S. Army Engineer Research & Development Center (ERDC) in Vicksburg, Miss.

He adds that it's also "a pretty potent reproductive toxin" in earthworms, noting that worms exposed to even minute levels of tungsten (700 milligrams of tungsten per one kilogram of soil) become infertile. Johnson says that the effects of tungsten on earthworm reproduction are “comparable” to that of lead in humans, which has been linked to neurological problems in fetuses and children.

So how much tungsten are people in the U.S. exposed to daily in their drinking water? No clue, says the U.S. Environmental Protection Agency (EPA). "We wouldn't know how much is in the drinking water system," says EPA spokesperson Enesta Jones, because it's not among chemicals on its list of known contaminants or regulated under the Safe Drinking Water Act.

ERDC geochemist Anthony Bednar told ScientificAmerican.com that scientists are trying to get a handle on the various chemical forms of tungsten in the environment, how they move through the soil – and whether any of them pose risks for people and the environment. Lab toxicologist Johnson, meanwhile, is trying to figure out how tungsten moves up the food chain—from its absorption by the plants (including agricultural varieties) to the animals and humans that eat them.

Image credit ©iStockphoto.com/Denis Vorob'yev

5 Comments

1. 1. speedevil 06:54 PM 1/20/09

   700 milligrams per kilogram is a _HUGE_ quantity in soil.
   It's one part in 1300 or so.
   
   To put this in context, this is around the equivalent of 40 100W light-bulbs full of tungsten.
   And that's per kilogram.
   That's practically the quantity per kilo you get if you crush a only lightbulbs.
   
   I'm not aware of any common growing systems that use crushed lightbulbs as a growing media. Soil or compost is rather more common.
   

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2. 2. iconoclasm 03:24 PM 1/21/09

   Human excrete tungsten more readily than lead. It's not like concern over tungsten is a new issue.
   
   http://www.cdc.gov/nceh/clusters/fallon/tungstenfaq.htm
   
   Tungsten can be found in some vitamins on purpose on the label.
   
   Also sodium polytungstate is thought to be non-toxic and is purchaseable. Excess sodium has negative effects as well. What type of polytungstate?
   
   I'm not suggesting that there should be no research or the opinons are unsound. I just need someone to connect a few dots on this one.

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3. 3. tlinget 05:49 PM 1/21/09

   I used to work in the drinking water business. It is not regulated by the EPA as of yet.
   I would guess to venture that tungsten occurs more naturally in nature that we currently contaminate.
   I had the honor and privilage of dealing with the EPA concerning the "contaminates" we were putting back into the environment when disposing of the sludge that resulted from settling and filtering the water. The EPA was charged with the authority to mandate where and how much sludge could be placed on farm land for land application.
   Land application of the material was chosen because disposal in a landfill was too costly. The EPA was charging us $9 a ton for use to monitor and dispose of our own sludge in our own landfill. We did all the testing and submission of reports. They sat back and collected the fees.
   The farm land upon which we were allowed to place this sludge had far higher levels of contaminants than the sludge we were disposing.
   

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4. 4. tlinget 05:51 PM 1/21/09

   CORRECTION:
   
   Tungsten is not regulated by the EPA as of yet.
   
   The water business is regulated by the EPA and state agencies. I do not wish to confuse anyone about that statement.

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5. 5. magmahombre 02:19 PM 3/13/09

   1 part in 1300 W is 769 ppm W or 980 ppm WO3; aqua regia soluble background W values are in rock and probably soils as well, typically are <3 ppm and often < 1 ppm so 769 ppm is a pretty high value; ore grade values in tungsten deposits of economic interest range from 500 ppm in large stockwork porphyry or greisen-type W deposits in which W is a coproduct or by-product metal (usually with Cu, Mo, or Sn) to 30,000 ppm in small, high grade skarn deposits and vein deposits though more typically skarn deposits large enough to mine range fro 3500 to 9000 pppm W

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