By Keith Roach, M.D.

DEAR DR. ROACH: How much mercury is safe? -- A.C.

ANSWER: The chemical element mercury exists in three forms: elemental mercury, which is the kind in thermometers; inorganic mercury, especially mercuric chloride; and organic mercury, including methyl and ethyl mercury. All of these have toxicities, but the types of toxicities are different for each, and the safe level depends on which type it is.

Elemental mercury is dangerous primarily when it is inhaled, which occurs mainly in occupational settings. Accidental swallowing of the small amount of mercury in a thermometer has very low toxicity, but I still don’t recommend it. Inorganic mercury is seldom a problem, as it is almost never used these days in the U.S. and Canada. Most products containing this form of mercury have been banned.

Methyl mercury is the major concern for consumers, as this is found in fish. It accumulates in the environment, and tends to be worst in larger fish, which eat the smaller fish and over their lifetime accumulate the methyl mercury, which was formerly used as a fungicide. The Environmental Protection Agency warns an average-size person not to exceed 70 mcg per day of methyl mercury: Below this dose, toxicity is unlikely. This translates to two to three servings of fish per week, but no more than one serving of highest-risk fish for methyl mercury per week. High-risk sources include most tuna, halibut and snapper.

Ethyl mercury is significantly less toxic than methyl mercury, as it is removed from the body more quickly. There is no EPA recommendation for ethyl mercury levels. Ethyl mercury has been used as a preservative in vaccines, but it has been removed from all childhood and most adult vaccines. It is still used in some flu vaccines -- the ones in multidose vials: Single-use vials do not need a preservative. The amount of ethyl mercury in a flu shot is less than the more dangerous methyl mercury found in a can of tuna.

Bipolar

DEAR DR. ROACH: Is it possible for a person to reach the age of 70 and just now be diagnosed with bipolar disorder? Are there degrees of impairment, like with autism -- some worse than others? -- C.S.

ANSWER: The hallmark of bipolar disease is mania. “Mania” has a specific meaning in psychiatry: It’s a very elevated mood, associated with high amounts of energy and an inability to think clearly, especially to see the consequences of one’s actions. Some common features of people in a manic episode include an inflated sense of self-worth, distractibility and racing ideas. People can be very talkative and feel little need to sleep. Dangerously, people in a manic phase can spend large amounts of money and have many sexual indiscretions.

All diseases have a spectrum of severity, and some are quite wide. With bipolar disease in particular, however, there are four distinct forms of the disease. Bipolar I is the classic form, once called “manic depressive illness,” where people have episodes of mania, alternating with periods of normal behavior or depression. People with Bipolar II have depressive episodes and some “hypomanic” episodes: periods of high energy (and sometimes profound productivity), usually without the negative aspects of the “full” manic episode. Cyclothymia is a rapid cycling between hypomania and mild depression. There is a fourth type, “unspecified,” where people have abnormal mood elevations but don’t meet criteria for the other types.

 Bipolar disease usually has its onset in early adulthood, but sometimes in teens or even childhood. However, I have rarely seen bipolar disease diagnosed in someone as old as 70. It isn’t always clear whether the disease is just manifesting that late, or whether it has been around for many years, but compensated for by the person. Some people don’t interact with a lot of family or friends, and manic or hypomanic episodes might be missed. It’s possible the 70-year-old in question has a quite mild form.

Treatment for bipolar disorder can dramatically improve the quality of life of the person and of the family and friends affected by the illness.

Dr. Roach regrets that he is unable to answer individual questions, but will incorporate them in the column whenever possible. Readers may email questions to [email protected]. (c) 2021 North America Synd., Inc. All Rights Reserved