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Hey, Matthew: Why can’t we have blue or green hair? We can have blue or green eyes, and isn’t melanin responsible for coloring our hair and our eyes? So why no blue hair? — Anonymous, via email

Why no naturally blue hair (or skin, for that matter) since, yes, melanin is involved in coloring all three of them? Well, let’s take hair first, since it’s simplest. Hair follicles contain two types of melanin: eumelanin, which comes in black- and brown-pigment types; and pheomelanin, a red pigment. Blue is not an option. Neither is green. All hair-shaft colors are made up of some genetically controlled combination of these two basic pigments, and both melanins can be present in a single follicle. That’s why, when you bleach dark brown or black hair, you get orange. The less-stable eumelanin is stripped away and the more-stable, harder-to-bleach pheomelanin is left. (Blond hair results from a very low level of the brown-type eumelanin). The genetic jury is still out on all the fine points of the expression of hair-color pigments, but those are the basics. Hair, eyes, and skin are genetically coordinated, making common combinations that we recognize (blond hair, pale skin, blue eyes), but our hair-color potential is limited to variations on the two melanins. Yes, unfair, I agree.

Eyes are a completely different matter, even though the same eumelanin is involved. Eye colors are created by light scattering through three layers of eye tissue: the outer pigmented layer, a layer of semi-opaque tissue, and an inner pigmented layer. In our eyes, we have a wider choice of pigments than in hair: brown eumelanin, yellow lipochrome, and blue. Eye-science guys have found at least six genes that control the expression of each of these pigments. They suspect there are many more, and the process is very complicated. But basically it’s the ratio of brown to blue to yellow and the distribution of the pigment in the iris area that give us our unique eye appearance. And because eye color is created by light reflection and scattering, it’s much more variable than is hair color, which doesn’t rely on light rays passing through layers of pigmented tissue. Blue eyes under one light condition might appear blue-gray under another. The expression of eye color is so genetically complicated that virtually any parents can produce a child with virtually any eye color. The odds might be slim, but the situation isn’t reliable fodder for gossip.

Hey Matt: I live in PB, and the homeless transients are always digging in the trash and eating out of it. How do they avoid E. coli when people go into the fine establishments and die from food being served there? Can I grow E. coli in my own trash can? — CG, via email

Well, it’s not like they’re heel-dragging E. coli victims out of George’s at the Cove every night. “Fine” establishments don’t kill customers any oftener than a taco truck does. In fact, an E. coli breakout isn’t all that common, no matter where the food comes from. About a quarter of a million people are diagnosed with the infection each year in the U.S., according to the CDC. I see what you’re getting at, but limiting the potential evils of dumpster diving to E. coli will make a trash can seem as safe as a professional kitchen. Sort of.

E. coli is a big, diverse group of bacteria that lives in the guts of cattle, sheep, goats, deer, and elk; but, once transmitted, it can survive in pigs, birds, and people. A toxin produced by the bacteria is what’s potentially harmful. Large outbreaks can begin at the farm end of the food chain — vegetables contaminated with infected manures or water. Slaughterhouses can introduce the bacteria into a meat product. The FDA is in charge of regulating food growers and processors to prevent all this, but obviously it does happen. But you can also get your own individual good dose from an infected restaurant cook who hasn’t been conscientious about hand-washing. So, you don’t have to be dipping in a dumpster to get E. coli. And the average poor soul who relies on trash for a meal isn’t at much more risk than the rest of us. And there’s been no E. coli epidemic in the Freegan community.

The diver, actually, is more likely to pick up hepatitis or some other such disease if he/she consumes food that a sick person has started to eat but discarded. Well wrapped, date-stamped food thrown out by a supermarket or the like is actually pretty safe (except seafood, meat, eggs, or raw milk, cheese, or juice).

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