Measuring mercury exposure (and why provoked urine testing is the wrong way to do it)

A commenter by the name of “Robin” asked for information on mercury toxicity a while back due to her husband having reported high mercury levels. My workload is finally getting close enough to being under control that I can tackle this. However, it’s a complicated topic with a few different aspects. Before I actually get into some of the effects of mercury, I think a bit of context is important. So for this first post I’m going to talk about how mercury exposure is measured and how to know if mercury levels really are elevated. I’ll follow that up with some future posts (hopefully within the next week or so) about where this mercury exposure is coming from, and what the effects can be [Update: part 2 on some causes of high mercury levels is here, and part 3 on the different types of mercury is here]. Some of the concepts in this post build on an earlier entry on measuring chemicals in blood and urine.

In order to understand any sort of testing for mercury levels in humans, it is important to understand what happens to mercury in the body. In general, mercury is distributed throughout the body after exposure; generally the highest levels end up in the kidneys and brain. Generally inorganic mercury has a half-life on the order of days in most tissues, but can stay longer in the kidneys and brain. Organic mercury, particularly methylmercury (the mercury compound of concern from eating fish), tends to stay in the body longer. Eventually both inorganic and organic mercury are excreted in urine and feces.

The most common way to measure mercury exposure is through urine samples, since it’s fairly simple to collect these samples. While it is total mercury (organic plus inorganic) that is usually measured, generally the results of urine testing are a better indicator of inorganic mercury than organic mercury. Both Health Canada and the US CDC have conducted population monitoring of mercury concentrations in urine. The average level in the US adult population was about 0.5 μg/L (just over 0.5 μg/g creatinine), but there was considerable variation; 95% of the population had levels less than 3.11 μg/L (2.31 μg/g creatinine) in 2005-2006. The Canadian data only reported inorganic mercury in urine; the concentrations were a bit lower, with 50% of the population aged 20-29 having levels less than 0.23 μg/L (0.2 μg/g creatinine) and 95% of this population less than 2.31 μg/L (1.93 μg/g creatinine); concentrations were similar in 60-79 year olds, but slightly higher in 40-59 year-olds. Other studies (summarized by ATSDR) have shown average levels in the range of 4-5 μg/L, however.

Some health practitioners (I use that term loosely here) have been using what is called a “provoked” urine test. This involves having administering a chemical to the person being tested that basically forces the mercury (and other metals) that are circulating in the blood, kidneys, and other organs to be rapidly excreted. The result is that the levels in urine are temporarily highly elevated (potentially around 10 times what they would be in an unprovoked test). The practitioners and labs using this test then tend to compare the results to the normal (unprovoked) range, making it look like the person has an unusually high mercury level, which is then often followed by recommendations for therapies or treatments to reduce the mercury level. This test should, for all intents and purposes, be considered a scam; even a normal person with an average level of mercury exposure will show up as having a high level of mercury. The only way you could meaningfully interpret the results would be to compare the results to reference ranges for provoked mercury in the general population, but there aren’t really good reference ranges for this, and there isn’t really a good reason to develop one since the test results aren’t particularly meaningful to start with. But if you want to persuade someone that they have high levels of mercury or other metals so you can sell them expensive and unnecessary treatments, this is the way to go.

Measurement of mercury levels in blood is also relatively common, and is also included in the Health Canada and CDC studies. Blood tests pick up more of the organic mercury, and in particular methylmercury; as a result people who consume a lot of fish tend to have higher levels of mercury in blood. In the US, average levels in blood are around 1 μg/L, and 95% of the tested population had a concentration less than 5.31 μg/L in 2005-2006. The Canadian levels were fairly similar in this case. ATSDR suggests average levels are around 1 to 8 μg/L, with a mean concentration of 2 μg/L for people who don’t eat fish, but this is based on older data; concentrations as high as 200 μg/L have been reported in people who eat a lot of fish.

Mercury exposure can sometimes be measured in exhaled air, but this is really only an indicator of very recent exposure to mercury vapours and only of use in some occupational settings.

Both blood and urine concentrations can fluctuate a fair amount and can be affected by recent high exposures. For measurement of longer-term (on the order of about a month) average exposures, hair samples are sometimes used. Mercury circulating into the body is incorporated into hair as it grows, and once there the concentration doesn’t change. Concentrations in hair have been found to correlate well with concentrations in organs where mercury may accumulate, such as the brain and kidneys, particularly for methylmercury. If you really want to evaluate whether someone has long-term high mercury exposure, particularly methylmercury, hair samples are probably a lot more reliable than blood or urine. However they can still be affected by airborne mercury vapours or some hair treatment products, and concentrations can also be affected by the rate of hair growth, and so these tests aren’t perfect either. The data on typical levels are also a lot more limited; the limited data suggest a concentration of about 0.25 μg/g, ranging up to about 2.5 μg/g, is typical in European populations, while in Japan levels tend to be more in the 2 to 4 μg/g range (presumably due to higher fish consumption). CDC measured mercury in hair of women and children in one of their surveys, and found generally consistent results, with median and geometric mean concentrations of about 0.2 μg/g in women and 0.38 μg/g in women who ate fish frequently.

The other approach to measuring mercury exposure is to measure how much mercury there is in various media that a person is exposed to. For example, mercury concentrations can be measured in the air someone breathes, the food someone eats, and the water someone drinks. This type of monitoring is more useful for occupational scenarios where a large number of people may be exposed to mercury-contaminated air in a single location, or for determining the average and range of mercury concentrations in a particular species of fish or fish from a specific lake (for example); testing all potential sources of exposure for a single person would be prohibitively expensive and impractical.

While there are several ways of measuring mercury concentrations in biological samples, it is important to stress that all of these methods can have highly variable results. Furthermore, and perhaps most important, while these tests (aside from the provoked urine test, which is completely unreliable), if done properly using standardized methods, may provide evidence about whether a person’s mercury exposure is higher than normal, a higher than normal mercury exposure does NOT automatically mean that the exposure level is harmful, particularly since most common tests don’t differentiate between the different mercury compounds (more on this in an upcoming entry).

20 Responses to Measuring mercury exposure (and why provoked urine testing is the wrong way to do it)

  1. […] the second in a planned series of posts relating to mercury exposure and toxicity (see also Part 1: measuring mercury exposure). In this part I’m going to look at some of the causes of high mercury levels measured in the […]

  2. I thought the information given was good.I am interested in knowing more for I work in the neon industry and have been around mercury for years. I might be a good source for study.
    I am interested in obtaining an air sampler device to read air vapor levels.

  3. ashartus says:

    Hi Dan. If you are interested in measuring vapour sample levels I’d recommend a Jerome 471 Low Level Mercury Vapor Analyzer, a Lumex RA-82 Prospector or a Lumex RA-915+ (based on research I did a couple of years ago; it’s possible there could be newer versions of these). These are among the few devices that can measure low-level concentrations with immediate results; there are other devices that can measure concentrations near occupational exposure limits in a sample that takes several hours to collect which are probably cheaper if you’re just interested in measuring occupational exposure (I tend to deal more with public health). It’s generally best to have someone who is familiar with mercury vapour sampling (e.g. an occupational hygienist) do the work and interpretation.

  4. Denise says:

    About 9 months ago my husband was driving around in his car for about 3 months (during winter) with a case of broken bulbs. Since then he has had muscle tremors, cognitive dysfunction, severe thyroid and testosterone imbalances…His doctors have not tested him because they said it was minor exposure. What do you recommend to be the best method for testing considering exposure was so long ago?

  5. ashartus says:

    Denise – there aren’t really any good ways for testing an exposure that long ago. A hair sample might give some information. The problem is that there isn’t really anything to compare results too for anything other than a (normal) urine test or a blood test, both of which are more reflective of recent exposures, and even those can only compare levels to the general population and don’t tell you anything about whether the level would have a health effect.

    Was it CFL bulbs? Do you know how many bulbs there were? If you have that information I could at least figure out what the worst-case exposure could have been.

  6. […] commenter on a previous post asked about potential mercury exposure from broken compact fluorescent lights (CFLs). There are […]

  7. Jeremy says:

    We tested our daughter for heavy metals. (6hr provoked urine test) the levels are compared to unprovoked levels. I think this is garbage. Is there any data so we can reference the levels we see against an average for others who have been “provoked” with DMSA?

  8. ashartus says:

    Jeremy, there are no reference levels for a provoked test – the results are unfortunately pretty much meaningless (except to fraudulent health practitioners trying to scam someone into unnecessary treatments for mercury toxicity). I’m not sure you could even develop meaningful reference ranges, since it would be affected by factors such as the provoking agent used, dosage, age/mass of the individual, etc.

  9. Connie Evans says:

    I’m 47 years old and I just had a 6 hour dmsa provoked urine test with the results saying that my mercury level is 28! It should be below 4. I’m really scared. Is this test really a scam? I trusted my naturapath doctor, but now I’m not sure.

  10. ashartus says:

    The 6-hour provoked urine test is completely meaningless, and should not be relied on in any way. I don’t think I’ve ever heard from someone with a level below 4 from a provoked urine test, and the 6-hour version is even worse than the typical 24-hour version. More often than not the provoked urine test is just used as a way to scare people into getting expensive and unnecessary treatments. Do you have a specific reason to expect high mercury (e.g. high occupational exposure)?

    • Connie Evans says:

      I have a couple amalgam fillings. I quit painting about 10 years ago when I did a lot of faux finish techniques where I had my hands in paint. Not sure if paint has mercury in it. About 24 years ago I did stained glass for a living for about 10 years, but I think that was only lead and tin which my lead was just slightly elevated and tin was fine. I eat salmon or tuna once a week. That’s all I can think of. My doctor said my level is so high they have to report it to the health department. That really scared me. I have a huge cancer and health phobias and read that mercury causes leukemia and hodgkins. Just not sure where to go from here. Thanks for your input and any info is appreciated.

  11. Connie Evans says:

    Also, have you heard of levels as high as mine, which is 28?

    • ashartus says:

      There isn’t any good information on what a “normal” level is since it’s not a legitimate test and the results are affected by things like what provoking agent is used, how much is given, duration of test, etc. but it’s within the range I’ve seen. One study a few years ago (unfortunately behind a paywall – abstract at looked at provoked urine test mercury levels in healthy people and people with symptoms that could be explained by mercury and found no difference. If you got that level on an unprovoked test I’d be worried, but the provoked test just can’t be related to any meaningful conclusions. It doesn’t sound like your exposures are anything out of the ordinary either. Also, mercury is not believed to cause cancer in humans – it’s effects are primarily neurological (not that that’s much better of course).

  12. Lisa says:

    My son has been sick since he was 13 years old. He is now 22 and we recently had a provoked 6 hr urine test. His level for mercury was 60. His primary physician had the 24 hour unproked urine test done and a blood test which resulted in very low levels for mercury. When I read the list of symtoms for mercury posioning, he has almost every one of them ( up to the point of permanent damage) including “buring brain” where we have to put ice packs on his head almost every night to bring the temperature down. He has not been able to work or go to school for 4 years. He has seen 13 different types of doctors that have no explanation for his systems except for the recent mercury test. My understanding is that unprovoked urine tests will detect current expose but does not detect the amount of mercury in the tissues which can lead to neurological problems (which my son is begining to show signs of). None of his doctors seem to think this is a big deal but cannot explain why he is so sick. Where do we go from here?

  13. ashartus says:

    You are correct that unprovoked urine tests only really evaluate short-term exposure. The provoked test is not reliable; do you have any other reason to suspect mercury? The general population isn’t really exposed to enough mercury to result in those kind of effects – they’re usually associated with high occupational exposures or other really unusual situations. The provoked urine test is generally used by unscrupulous practitioners to convince people they are suffering from metal toxicity and sell them on treatments like chelation therapy (which is fairly dangerous) – I’d be very careful about drawing any conclusions from it unless you have reason to believe your son has been exposed to abnormally high levels of mercury in the past. The symptoms of mercury poisoning you mention can also be symptoms of other neurological problems – unfortunately it’s very rare for a specific symptom to be associated with only one thing. I can’t really tell you where to go from here – I don’t know enough details, and I’m a toxicologist, not a doctor.

  14. Margery Riggans says:

    Blood test can reveal some health conditions. That is why it is always a good idea to get some periodic blood test. ..

    Please do browse this useful homepage

  15. John says:

    How long after an elemental mercury vapor exposure would urine tests still be useful. Also how long in blood.

  16. patricia G says:

    I had about 13-15 silver (poison) /mercury amalgam fillings removed with great expense and inconvenience but it was worth it all! I had been having pains in my hands and joints and been told that it was probably the start of arthritus- well, I took my preventive doctor’s advice and had my gold and silver fillings removed-going all the way to Calif from Missouri- after reading and doing all my “homework” on how these amalgams had to be removed…it will be two years in Dec. 2013- and the pains have been gone and my joints no longer ache and burn! Best medical move ever- even though I am not fond of dentists and go to them regularly out of fear of having bad teeth and dental caries! Now I go only to dentists who have a firm stance on NOT placing these mid-evil fillings into the mouths of their patients!

    • Syl says:

      Thanks for sharing your post. I have been ill with chronic fatigue syndrome since since Oct. 2010 (and probably even before then) becoming bedridden for six months in May 2011. On my last visit to the nutritionist, she suggested mercury poisoning as all the treatments we have tried have not alleviated my fatigue. I am currently testing as I write. I am having every symptom I had when I became bedridden in 2011 only to a lesser degree. I expected to feel this way and was scared to do it. I’m now more convinced mercury poisoning is my problem. My mercury exposures are 12 amalgams and a pneumonia vaccine in March 2010 (and before the administrator of this site comments on vaccines not containing mercury, I don’t believe you. Dr. Oz does not vaccinate his children for that reason). Once I get my test results, I will begin removing the fillings I’ve had since childhood and chelate thereafter. I would say to anyone confused about the advice on this site, please listen to your body! Only you know what is right for you. I would probably still be bedridden if I hadn’t poopoo’d my conventional doctors diagnosis of “conversion disorder” and sought alternative therapies. There are too many testimonials of people ridding their systems of mercury only to feel better than they had in years. This site is shameful and makes me wonder who is backing it.

  17. voyance says:


    Measuring mercury exposure (and why provoked urine testing is the wrong way to do it) | exposure/effect

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