I’ll leave it to political reporters to explain why, of all the cringe-inducing business dealings that Mark Penn kept his hand in as chief executive of the PR titan Burson-Marsteller even as worked for Hillary Clinton’s presidential campaign, it was his work on behalf of Colombia to secure passage of a bilateral trade agreement with the U.S. that led to his downfall. Yesterday he quit as Clinton’s chief political strategist, though he’ll stay on as a pollster.

I have no idea whether a Colombian trade agreement would be good for the U.S. But I do know that Burson-Marsteller’s work on behalf of the high-mercury fish industry is an excellent way to get even more neurotoxins into babies’ developing brains. Burson-Marsteller has worked tirelessly to persuade people—especially pregnant women—that the mercury that tuna (especially albacore) is laced with is nothing to worry their pretty little heads about.

Last year, the New York Sun reported that it had obtained Penn’s internal blog entries, including one from Dec. 20, 2006, in which he brags about landing the U.S. Tuna Foundation’s PR business. His company pitched “ideas for how to act like a political campaign by neutralizing the negatives and bringing out the heart healthy benefits of tuna,” Penn wrote, according to The Sun.

The issue of mercury in tuna makes the industry apoplectic (as you can see from its response to an earlier blog item). But Clinton had, as a senator, stood with those trying to protect children, not the industry, when she signed a 2004 letter criticizing the Environmental Protection Agency for soft-pedaling its own advisory about mercury in fish (especially albacore tuna, since canned tuna is the fish Americans eat more of than anything other fish besides pollock), which “specifically informs women that they and their young children should limit consumption of tuna.”