Baltimore is like a bowl, with four major rivers flowing through the city down to the harbor. These rivers have become almost open sewers because the old sewer lines laid along them are all cracking and leaking. Sampling has been done, looking at microorganisms in the streams, and some of these microorganisms are pathogens. Who is exposed? Fishermen.

The EPA doesn’t issue fish advisories on pathogens because people cook the fish and that takes care of it. What’s the big deal? But we started to study this, and one day I’m out fishing with two retired bus drivers, just below Lake Roland. We’d been there a couple of hours when one of my companions reaches into his pocket and takes out a sandwich, breaks it in half and offers some to me. I look over at my other friend, and he’s smoking a cigar.

All of a sudden I think, Wait a minute, this is not about consuming fish. This is about the fact that my hand has been in the water, that I’ve grabbed a catfish, taken it off the hook, put it in a bag. And now I’m going to eat something [using my hand]. This is about fish as a vector of pathogens not because they’re infected but because they’re objects.

I went back to my student, Jennifer Roberts, and said we’re going to find out what’s on the fish, not what’s in the fish. We looked at some fish wipes, and it turns out these fish are carrying—on their surfaces—all kinds of dreadful things. This is going to have an enormous impact on how we do risk assessment. No one has ever made this connection before.

I’ve fished all of my life. And whenever I tell this story people say, “Of course!” It sounds obvious. That’s why I cite this story to my students. The message is: Always be observant. Sometimes you just have to be out there to understand what’s going on.