What's the difference between having mercury exposure and mercury poisoning?
A lot of this has to do with numbers versus symptoms. Just because you're exposed to a toxin doesn’t mean you get poisoned. You can build up a blood or tissue level but not yet manifest symptoms related to poisoning. Call it a threshold.
A person with no symptoms, no changes physically or chemically, we just say they've been exposed and have a high mercury level. It doesn’t become poisoning under the true definition unless someone has had physical or chemical changes in his or her body. It's a very fine distinction, but one person is symptomatic and the other asymptomatic. The person who is symptomatic is poisoned. The one who is asymptomatic has a high blood level consistent with exposure.
That doesn’t mean it's safe to have levels without symptoms. Over time, even if you're exposed at low levels, the symptoms may not manifest until weeks or months later.
A person can find out if they had a higher-than-normal exposure — the urinary level is the most specific way. Blood levels can also be used, and we plot those against your geographic area.
What are the symptoms of mercury poisoning?
Symptoms can occur in many ways. Unfortunately in mercury, symptoms can look like many disease states. When levels are building up, there could be a variety of symptoms that a physician may interpret as another illness. Only when the physician can't find a real cause or gets a toxicologist involved will they do blood tests and say, "Yes, this is probably due to mercury exposure."
It's a difficult diagnosis. You have to know by history that a person has been exposed to this and put two and two together. No specific set of symptoms will say, "Ah, this is mercury poisoning."
If it's mercuric salts the person has been poisoned by, it may just be a problem with the kidneys, issues with the ability to urinate, or they're feeling out of whack because of renal dysfunction.
If someone is inhaling fumes from elemental mercury, that can show up as an upper respiratory illness, like a flu, at first. They might find they can't concentrate well, have trouble with fine motor control or their perception of smell, eyes or touch. If it was affecting their heart, it could be palpitations or just in general not feeling well. If something is not going well with their blood cells forming, they may have issues similar to anemia, feeling very tired, easy bleeding or bruising.
With organic mercury exposure, the symptoms are pretty much the same, but probably not respiratory. The nervous system effects are what someone would see first.
How would mercury toxicity or poisoning be treated, and how long would it take for someone to get well?
What is used, when, and how is decided by a doctor on case-by-case basis in consultation with a toxicologist. If you do have high levels, the first thing to do is stop the exposure.
Chelating agents make metals more water-soluble so they can be excreted by the kidneys. That works fairly well for inorganic salt forms of mercury poisoning but not so much for neurologic forms from the elemental.
There are old World War II antidotes, actually: Injectables are used when we have high levels and only when we don’t have the organic form of mercury poisoning; it's the elemental and inorganic poisonings that we use them in. British anti-Lewisite (BAL), or dimercaprol, is one of these agents: it's an antidote the British developed against lewisite gas, and it's a potent chelator used against mercury, arsenic and lead.
If it's eating too much fish, we stop them from eating the fish and get the levels to come down naturally. Otherwise, there's nothing we can do.
How long treatment takes has to do how high the level is and how chronic the exposure is. If it's somewhat low levels, chelating might happen relatively quickly. If it's exposure for many years, it may take longer for those levels to come out.