Mercury in single malt whisky is something about which you should never be concerned. Seriously, don’t worry about it. A recent study tells us that even the most highly contaminated bottles are more than 600 times lower than the World Health Organization’s current guideline for acceptable levels of mercury in drinking water. That’s for something you drink by the tablespoonful versus something you drink by quarts or liters. There is nothing to worry about here.*
So why bother talking about it, or measuring it in the first place? The authors behind that study were following up on a medium-sized hullaballoo in the mid-1990’s over relatively high concentrations of polycyclic aromatic hydrocarbons (PAHs) in single-malt. If that acronym looks familiar, it’s likely because PAH’s are the reason for the shadow cast over our grilling habits and, if I die of cancer, a probable place to point the finger.** PAHs are carcinogens formed by incomplete combustion that gives off smoke; in other words, PAHs are a minor-but-maybe-significant component of that marvelously flavorful char that accumulates on the outside of your barbecue, part of what makes smoked salmon such a very worthwhile thing, and one of the many reasons why cigarettes are a really nasty habit. It’s logical to suspect that they might be part of smoky single malts, too, which a group of researchers did strongly enough to bother studying it.
Chemistry confirmed the logic: moderate concentrations of carcinogenic PAHs showed up in the Scotch. But it also found something else. Single malts were worse off than American bourbons or Irish whiskies and even than blended Scotch. Worse yet, from my perspective, they found the highest concentrations in Laphroig and Oban, two of my favorites. Drinking whisky is associated with increased risk of colorectal, esophageal, and mouth cancer in the sorts of studies that measure such thing, though the researchers said that the concentrations of PAHs they found weren’t high enough to explain those risks.
So why the leap to mercury? Whiskies from southern Scotland turned up with higher PAHs than whiskies from northern Scotland. It’s well known that the south and west of Scotland is subject to more pollution than the north and east; it’s changing, but coal- and oil-burning proportionally overload the southwest with various airborne unpleasantries that end up migrating to soil and water and, evidently, to whisky. But maybe those Islay whiskies weren’t high in PAHs because of their proximity to the more densely populated and polluted parts of the country (and England). PAHs could just as easily come from those peat-smoked malts or the oak barrels used for aging.
If whisky’s carcinogens are a function of environmental pollutants, then concentrations of other environmental pollutants should follow the same south-north gradient pattern. And so we have the mercury study. Mercury levels in every whisky they tested were far too low to cause concern, but they nevertheless followed that same pattern: higher in the south, lower in the north.
This is a good thing, even for me and the rest of the hyper-peated club. Environmental pollutants from coal and oil combustion have declined massively, more than 90% since 1970, and continue to fall. Off-the-shelf whiskies the chemists tested were at least 9 years old, reflecting the environmental conditions of a decade or so ago. Tracing carcinogens to those conditions rather than to part of the whisky-making process itself means that it’s becoming less hazardous all the time. Or, at least, less hazardous in this one respect. Anything as delicious, expensive, and high-octane as a good single malt is always going to be at least a little dangerous.
*In light of recent events, I feel the need to make myself perfectly clear on this point.
**My diet is pretty ridiculously high in fruits, vegetables, whole-grains and all of those things we’re told should protect us in times of cancerous trouble, but I have an abiding weakness for smoked and charred foods. And I spend a lot of time with candles and incense, and I’m Catholic, which evidently doesn’t help.
***Which warrants quoting in full a letter to the editor sent to the Lancet following up on the PAH study:
As a member of the Scottish Malt Whisky Society, I found Kleinjans’ (Dec 21/28, p 1731)1 report of polycyclic aromatic hydrocarbons in whiskies of interest, but have one question. Since the authors used only 200 mL of each of the 18 whiskies studied, what did they do with the remainder? I hope that they had a very merry Christmas.