Tel: +44 20 8996 2221
Fax: +44 20 8994 8728
Email: info@itia.info
INTERNATIONAL TUNGSTEN INDUSTRY ASSOCIATION
Information on tungsten: sources, properties and uses
Health & Environment
Research on the health and environmental effects of tungsten has been conducted by various national and international organizations. While all chemicals and metals can cause adverse effects at high enough concentrations, these studies indicate that tungsten has a low potential to cause harm to animals and humans at environmentally relevant concentrations. Several of these studies are on-going. As with all metals, appropriate care must be exercised when processing and using tungsten and tungsten substances. To assist its members and the industry as a whole, ITIA set up the Tungsten Consortium to compile the necessary registration dossier required by the EU REACH regulations. After reviewing and assessing relevant hazard data, the Technical Committee of the Tungsten Consortium arrived at the following hazard classifications for the major tungsten substances found in commerce:
| Substance | Hazard Class (EC 1272/2008) | Hazard Warning |
|---|---|---|
| Ammonium Metatungstate | Acute oral toxicity 4 | Harmful if swallowed |
| Ammonium Paratungstate | Not classified | None |
| Sodium Tungstate | Acute oral toxicity 4 | Harmful if swallowed |
| Tungsten Powder (0.6-0.9µm) | - Flammable solid 1 - Self-heating 2 |
- Flammable solid - Self-heating in large quantities; may catch fire |
| Tungsten Powder < 5.25 µm | Flammable solid 1 | Flammable solid |
| Tungsten Powder > 5.25 - < 9 µm | Flammable solid 2 | Flammable solid |
| Tungsten Powder >9 µm | Not classified | None |
| Tungsten Blue Oxide | Not classified | None |
| Tungsten Carbide | Not classified | None |
| Tungsten Disulphide | Not classified | None |
| Tungsten Trioxide | Not classified | None |
Since tungsten products in the form of articles are very hard and abrasion resistant, they can be used safely by consumers as there is very limited potential for tungsten exposure.
Tungsten is a strategic metal and, as such, sustainability of tungsten resources is critical. Scrap recycling is an important factor in the world’s tungsten supply. Due to its high tungsten content by comparison to ore, tungsten scrap is a valuable raw material It is estimated that today some 35% is recycled and the tungsten processing industry is able to treat almost every kind of tungsten-containing scrap and waste to recover tungsten and, if present, other valuable constituents. In addition, by-products generated during tungsten production, such as ammonia, are routinely recycled.
Tungsten compounds are used in several applications that provide environmental benefits. For example, various tungsten species are used to prepare catalysts for use in the petrochemical industry. These catalysts serve to improve the yields of highly desirable components in gasoline and reduce environmentally harmful by-products, such as sulfur and nitrogen compounds. More recently tungsten compounds have found increasing use as a catalyst for the reduction of nitrogen oxide emissions from exhaust gases. Tungsten compounds also have potential clean energy applications such as photovoltaic cells and fuel cell technologies. For more information on Tungsten for a Cleaner Environment, see ITIA Newsletters - June 2004 and December 2004.
Results of the Hardmetal Epidemiology Study - an International Investigation
In December 2017 a series of papers detailing the results of an extensive epidemiological study of hardmetal workers were published in the Journal of Occupational and Environmental Medicine. The study included 32,354 workers from three companies and 17 manufacturing sites in five countries. The University of Pittsburgh Center for Occupational Biostatistics and Epidemiology coordinated the studies which involved researchers from ten different institutions in Europe and the US. Based on the pooled data, the researchers found no evidence that duration, average intensity or cumulative exposure to tungsten, cobalt or nickel, at levels experienced by the workers examined increases lung cancer mortality risks. They also found no evidence that work in these facilities increased mortality risks from any other causes of death. Click here for a summary of the study methods and results prepared by the study's lead reseacher. The following is a listing of the published peer reviewed papers:
- Mortality Among Hardmetal Production Workers: Pooled Analysis of Cohort Data From an International Investigation. Marsh GM, et al. J Occup Environ Med. 2017 Dec; 59(12):e342-e364.
- Mortality Among Hardmetal Production Workers: A Retrospective Cohort Study in the Austrian Hardmetal Industry. Wallner P, et al. J Occup Environ Med. 2017 Dec; 59(12):e282-e287.
- Mortality Among Hardmetal Production Workers: UK Cohort and Nested Case-Control Studies. McElvenny DM, et al., J Occup Environ Med. 2017 Dec; 59(12):e275-e281
- Mortality Among Hardmetal Production Workers: Occupational Exposures. Kennedy KJ, et al. J Occup Environ Med. 2017 Dec; 59(12):e297-e305.
- Mortality Among Hardmetal Production Workers: The Swedish Cohort. Westberg H, et al. J Occup Environ Med. 2017 Dec; 59(12):e263-e274.
- Mortality Among Hardmetal Production Workers: German Historical Cohort Study. Morfeld P, et al. J Occup Environ Med. 2017 Dec; 59(12):e288-e296.
- Mortality Among Hardmetal Production Workers: US Cohort and Nested Case-Control Studies. Marsh GM, et al. J Occup Environ Med. 2017 Dec; 59(12):e306-e326.
- Mortality Among Hardmetal Production Workers: Swedish Measurement Data and Exposure Assessment. Westberg H, et al. J Occup Environ Med. 2017 Dec; 59(12):e327-e341.
- Cancer Incidence Among Hardmetal Production Workers: The Swedish Cohort. Svartengren M, et al. J Occup Environ Med. 2017 Dec; 59(12):e365-e373. Free full text
National Toxicology Program (NTP) - Sodium tungstate Toxicology and Carcinogenicity Testing
In 2002 Sodium tungstate was nominated for testing under the National Toxicology Program by the Center of Disease Control, National Center for Environmental Health. The testing program included a 3-month dose range finding study and a definitive 2-year drinking water study using rats and mice exposed to sodium tungstate dihydrate via drinking water. The studies in rats included a perinatal component in which female rats were exposed throughout gestation and lactation and first-generation offspring continued in the study after weaning. In the 3-month studies the animals were exposed to 125, 250, 500, 1000, or 2000mg/L; in the 2-year studies the rats were exposed to 250, 500, or 1000 mg/L and mice to 500, 1000 or 2000 mg/L.
The NTP issued the final report of its findings in November 2021. When evaluating the study results, the NTP places the evidence of carcinogenicity into one of four categories: clear evidence of carcinogenic activity, some evidence of carcinogenic activity, equivocal evidence of carcinogenic activity, and no evidence of carcinogenic activity. The overall conclusions (which were ratified by a review panel on April 2, 2021) from the studies with respect to the carcinogenic potential of sodium tungstate at the exposure concentrations are as follows:
• There was no evidence of carcinogenic activity of sodium tungstate dihydrate (ST) in male rats.
• There was equivocal evidence of carcinogenic activity of ST in female rats.
• There was equivocal evidence of carcinogenic activity of ST in the male mice.
• There was no evidence of carcinogenic activity of ST in the female mice
(Note: equivocal evidence of carcinogenicity is concluded when the studies are interpreted as showing a marginal increase of neoplasms that may be chemical related.)
With respect to reproductive toxicity, in the Perinatal and Two-year Study in rats, there were no significant effects on reproductive performance, including the percentage of mated females producing pups. During gestation and lactation, the mean body weight of dams in the 1,000 mg/L group was lower than that of the vehicle control group. There were no exposure-related differences between the vehicle control group and the ST exposed groups in the number of litters, litter size, mean litter weights, sex ratio, or the pup mean weights of males and females.
Details of the studies and findings can be found in NTP Technical Report TR 599: Toxicology and Carcinogenesis Studies of Sodium Tungstate Dihydrate (Drinking Water Studies).
ITIA members are encouraged to login the ITIA Members' Area and find more details on the ITIA HSE Work Programme webpages and HSE literature database.