What’s important about last week’s David Letterman story isn’t sex -- it’s pollution.

Like many fans, I thank Letterman for making me laugh and feel his personal life is up to him. But how he - as a powerful man - behaves at work is not a private matter. Taking up with underlings is like dumping small amounts of sludge. Many people want to look the other way, like it doesn’t matter; but when the downstream impact seeps in to your own life, you have a different view.

Workplace Romeos can sometimes be funny. A law firm partner could not decide between his secretary and one of his young female associates -- so he maintained his affairs with both. “There was so much drama, I couldn’t work at that firm,” a young woman lawyer said. Plenty of office romance is the two-way, consensual, peer-to-peer kind. Sometimes it even ends in happy unions. But when senior guys find girlfriends among subordinates, they create externalities like fears of favoritism, uncomfortable colleagues and copy cats. (See Randy Cohen of the NYT for his take on this.)

OK-to-play currents at the office also mess with minds. In college, I worked for a good guy who was like my big brother -- until he decided to pin me one night with a large drunken kiss. It took me only minutes to remind him of his wife, my boyfriend, the fact that letting go of me was a really good idea. My boss apologized the next morning -- while telling me I’d made a mistake for turning him down. Decades later, when younger women tell me similar tales I remember this: That encounter left me less sure about a lot of things. Where I should work, whom I could trust, how I saw myself.

In focus groups for our book, Getting to 50/50, we heard many hopeful stories -- firms that set clear rules, male and female bosses who keep their workplace G-rated. But we’re sad to see young women, from consulting to academics to medicine to business, still coping with the toxins when polluters aren’t reined in.

An engineering student in her 20s told me how she won a spot in at a prestigious firm. But she left when a 40-something boss kept coaxing her to see his Hampton house -- while his wife was abroad. How much energy would she have to expend deflecting advances? Why was this her job? With a bad taste about big firms, this young engineer set up her own outfit where she could set the culture. Guys who confuse the office with a dating service drive out a lot of talent.

With the slow pace of change, my 5-year old daughter will still have a lot of muck to get through when she starts work. So I’ll try to give her good radar for guys with boundary problems and suggest she plant her romantic life away from the office. And I’ll be tempted to stamp her resume: “HANDS-OFF MANAGEMENT ONLY (or her mom will kick your ass)!”

And what will I say to my son? When powerful men make the office their play pen, they inspire a lot of envy. Easy access to fun sounds great. I’ve had a few guy friends fall prey to the view that workplace womanizing is a status symbol -- one they want. Like my friend Joe whose eyes would fill with glee regaling me with tales about his politico-boss and wild times with willing gals at work. Joe got elected and enjoyed the bounty, if on a more modest scale than his old boss. Until someone found out and Joe lost it all -- job, life with his family, reputation. I hope Letterman fares better.

Maybe I can just tell my kids the story of Fred, a successful man I really admire. After a lot of romantic friction in a company he owned, Fred put a new guy in charge saying: “Let’s be clear: 50 people work inside this company. Millions work outside it and many are attractive women. If you want a date - go find her out there.” A few crisp words can do lots to clean the environment.