OUR VIEW YOUR VIEW

How much poison in a ‘safe’ fish? It’s no use asking Ottawa

WALTER STEWART August 1 1970
OUR VIEW YOUR VIEW

How much poison in a ‘safe’ fish? It’s no use asking Ottawa

WALTER STEWART August 1 1970

How much poison in a ‘safe’ fish? It’s no use asking Ottawa

WALTER STEWART

Of course I’m sure the fish is safe

— all I said was, “Can I have

chicken instead?”

One thing about mercury is that it is highly toxic: it can cause tremors, numbness, blurred vision, deafness, diarrhea and, sometimes, death. It can also cause mental instability, and the expression, “mad as a hatter” comes from the fact that many workers in the hat industry, where mercury was once used extensively, went insane from inhaling its vapors. Mercury is no longer used in the manufacture of hats, but it is widely used in other industry and winds up, occasionally in dangerous quantities, in our rivers and lakes.

Another thing about mercury is that nobody seems to know exactly how much of it is bad for you. Oh, we know generally that a little bit is a little bad, and a lot is very bad, but at what point should people be forbidden to eat mercury-contaminated foods? There is a figure, of course — there is always a figure. It is 0.5 parts per million. When fish contain more than 0.5 ppm in their tissues, the government steps in, seizes the catch and, if necessary, closes down the fishery. (Fisheries are closed pretty quickly — the heavier polluting industries are closed more slowly, if at all. The logic seems to be that if somebody is going around poisoning the apples, the fair thing is to put the orchard-

owner out of business.) But this 0.5 ppm, comforting as it sounds, doesn’t mean anything. It is merely what the federal department of health and welfare, which set it, calls an administrative figure. A guess, if you like, at a safe contamination level. Now it turns out that the guess is based on bad information, and the acceptable level may be nearly three times too high.

That, at least, is the argument put forward by a scientist in the fisheries research board, Dr. John B. Sprague. Sprague’s thesis has not been popular with the government, since it suggests that much of the fish now considered safe may not be safe at all. The circulation of his paper, “Spot Checks On Mercury Residues In Some Fishes From The Canadian Atlantic Coast,” has been sharply limited. He has been asked, indirectly, not to discuss his findings with the press, and a stiff note went to his superior at the St. Andrew’s Research Station objecting that Sprague’s paper was “hardly reassuring to the Canadian public or to the fishing industry.”

Quite right, since I have read the paper, released by a reluctant but resigned department of fisheries, and I am not reassured. Sprague and an assistant analyzed a small number of fish from the Atlantic region, and found that they contained between 0.1 and 0.4 ppm of methyl mercury — below the danger standard. But Sprague used his sample, which he admits is too small to indicate general levels of mercury pollution in the area, as a springboard from which to attack the standard itself.

The acceptable level was established after studies on the bodies of 111 Japanese villagers who died from eating mercury-contaminated fish, showed an average level of 50 ppm. In accordance with normal toxicological practice, that figure was divided

by ten to arrive at a level which should be safe from lethal effects — 5 parts per million. Dividing by 10 once more provides a figure of 0.5, which should be safe from all effects, lethal or sub-lethal.

But the whole exercise was based on miscalculation. The amount of mercury in the Japanese bodies was measured on a dry-weight basis, whereas about 80% of the human body is water. In fact, the starting figure would have been 10 ppm, not 50, and, Sprague suggests, a safe level — if there is such a thing — might be closer to 0.2 than 0.5. (He got this by starting with a figure of ten, dividing by ten for lethal effects and by five for sub-lethal effects. Since nearly half the fish he studies exceed the 0.2 level, the implications of Sprague’s argument are clear and ominous — we may be eating unsafe fish.)

I raised this point with both the department of fisheries, where I was told, “We don’t set the figures, we just apply them” and the department of health, where I received a curiously ambiguous response. In the first place, I was told by a spokesman who remains discreetly anonymous that “Canada was well aware of the socalled miscalculation when we set our safety standards.” However, in the second place, “You may be able to make quite a good argument about whether 0.2 is a better figure than 0.5” and, in the third place, “There may be some changes made in this regard.”

What that seems to mean is that without ever admitting to a mistake, the government is now about to correct it, hopefully before anybody gets hurt, and that fish you are eating, which is perfectly safe today, may be more than 200% over the safety standard tomorrow.

Mad as hatters, all of them. □