When we talk about trace heavy metals, many of us consider their toxicity because they can damage our organs, while others think about them as nutrients (link to the introduction of The Nutritional Trace Metals publication), because our body needs them for normal metabolism. But, we need a balance when ingesting these trace elements, as too much or too little will not do any good (link to a review abstract for trace metals).
In my previous blog post, Top Four Toxic Metals in Water: Facts and Testing (link to the post), I discussed the toxicity of arsenic, cadmium, lead, and mercury. They are very toxic and have no nutritional value; however, they are not the only toxic metals (link to the EPA National Primary Drinking Water Regulations page) we should be concerned about. Under the 1996 Safe Drinking Water Act Amendment, every six years all of the > 90 drinking water contaminants are reviewed by the EPA to determine if the regulation needs to be modified.
In addition, under the same amendment, every five years, the EPA is required to review no more than 30 unregulated contaminants through the Unregulated Contaminants Monitoring Rule (UCMR). The EPA decides if new regulations for drinking water will be issued based on the occurrence of contaminants in public water systems and adverse health effects. Under the most recent UCMR3, five metals were listed on the UCMR3 list for further evaluation: cobalt, molybdenum, vanadium, strontium, total chromium, and chromium (VI). In two previous blogs, I reviewed the UCMR3 results on strontium (link to post), and total chromium, and chromium (VI) (link to post).
In this post, I am pleased to update you on monitoring of cobalt, molybdenum, and vanadium monitoring in the UCMR 3 program. If you’d like to know more about UCMR3 metals and about vanadium speciation in drinking water, you might like to join us for an upcoming webinar (June 30), Rapid Speciation and Determination of Vanadium Compounds in Water Samples, (link to registration page). In case you are reading this post after June 30, the webinar is available on-demand at the same location.
Health Facts on Cobalt, Molybdenum, & Vanadium
All these three metals are sold as trace nutrients (link to a trace nutrient site) because of their health benefits, but they may also adversely affect health.
Cobalt is part of vitamin 12, which is required for myelin formation and is used to treat anemia because it stimulates red blood cell production. But, cobalt can be toxic; for example, inhaling cobalt leads to respiratory problems. Although, cobalt toxicity is not a result of normal drinking and eating, together with nickel, cobalt can accumulate in the body and cause asthma, anxiety, and cardiac symptoms. Drinking too much beer containing cobalt as foam stabilizer over many years may also have adverse cardiovascular effects. However, the data about cobalt’s effect on cancer are limited.
Vanadium and molybdenum are associated trace elements. Molybdenum has been proven to be an essential element for humans and acts as a co-factor for several classes of enzymes. Low levels of both vanadium and molybdenum may cause spinal degeneration. Molybdenum is available in many types of vegetables; however, chronic exposure to high levels of molybdenum increases the serum uric acid level and may cause gout-like illnesses, according to the Centers for Disease Control (link to the website). Vanadium, on the other hand, is a possible carcinogen, according to the International Agency for Research on Cancer.
Although all three metal elements are important for health, they have risks if more than a certain amount is taken. Currently, the health reference concentration (links to the EPA glossary) for cobalt, vanadium, and molybdenum has been set to 70 ug/L, 21 ug, and 40 ug/L, respectively. Together with the reference dose, the reference concentration is used in the EPA’s non-cancer health assessments.
Occurrence of Cobalt, Molybdenum, & Vanadium in Public Water
From UCMR3 data summary (downloadable PDF) , we see more than 4.90%; 20.26%; and 73.14% of public water systems have detected cobalt, vanadium and molybdenum, respectively, above their corresponding minimum reporting level (MRL) at 1 ug/L, 0.2 ug/L and 1 ug/L. The EPA UCMR3 program will continue collecting the results until Dec. 2015 and will make regulatory decisions thereafter.
Analysis of Cobalt, Vanadium, & Molybdenum
Under the UCMR3 program, all five metals are required to be analyzed using the EPA 200.8 method and chromium (VI) using EPA 218.7. You can find how these UCMR3 metals are analyzed using the 200.8 method (downloadable application note) with ICP-MS (Thermo Scientific iCAP Q ICP-MS system).
The EPA 200.8 method detects only the total elemental concentration, but not for individual species or speciation. Although many labs are doing speciation work on multiple elements (link to the application notebook on speciation), such as chromium, selenium, arsenic, and mercury, using mainly IC-ICP-MS (link to the speciation web site) or HPLC-ICP-MS, there is no regulation requiring elemental speciation. The EPA and American Society for Testing and Materials (ASTM) have developed only a couple of speciation methods, such as EPA 321.8 for bromine speciation and D6994-04 for cyanide speciation.
Leave your thoughts about heavy trace metal analysis below; I look forward to hearing from you.