I am an OB/GYN by training. I am a guycologist by default. It started 20 years ago, when I had two boys and quickly learned that my shy husband was not going to make an effort to explain male vs. female anatomy to curious little children. I was the one who showed them Gray’s Anatomy textbook and taught them the anatomically correct names for all the sexual organs.

As teens I gave them the “condom talk,” which I took very seriously. I timed them to make sure they could unfurl a Trojan onto a banana in less than 20 seconds. I didn’t care if they rolled their eyes 500 times. I was not going to be a grandmother while they were still in high school.

But it was one of my male friends who coined the term “guycologist” to describe this strange role that my expertise in (mostly female) reproductive anatomy created for the men in my life. Often I would find myself being quizzed by men on the risks of using Viagra, or their worries about prostate cancer. Usually this happened after they had consumed a few alcoholic beverages. Many of my patients’ husbands or boyfriends have also asked me these questions — even though they (presumably) aren’t drinking in the clinic waiting room.

Now that I study reproductive environmental health, I feel that my role as a guycologist has broadened. I’d like to discuss the emerging science around the environment, and what it means to be a guy. (I will add this caveat: when it comes to human disease and the environment, causality is difficult to prove because of genetic susceptibility and the timing of complex exposure patterns.)

First, as your guycologist, I’m warning you: if you’re a man with a history of infertility, keep an eye on your junk. There are very strong associations between infertility and future testicular cancer. [PDF] Be especially careful if you think you were exposed to pesticides in utero or early childhood. Testicular cancer may be related to early pesticide exposure. So is prostate cancer.

If you’re a man interested in reproducing, sad news. Both sperm counts and testosterone levels have declined in the last 30 years.

If you’re a man who likes to have other men around, sad news also: There are fewer men than there used to be. Scientists know that the worldwide birth ratio of boys to girls is 106: 100, but in some populations there have been drastic declines. For example, in the Canadian Chippewa First Nation, the ratio has declined to 1/3 boys: 2/3 girls.

We know from animal science that several chemicals disrupt testosterone balance by either blocking testosterone or increasing estrogen. Male alligators exposed to a 1980 toxic pesticide spill (dicofol and DDT) in Lake Apopka, Florida were demasculinized, and there was a dramatic decline of the American alligator population compared to a nearby uncontaminated lake. Numerous studies by Dr. Tyrone Hayes and colleagues from UC Berkeley have shown that at least two species of male frogs exposed to dilute amounts of atrazine, the second most commonly used pesticide in the United States, exhibit malformation of male sex organs and/or development of female sex organs.

I’ve also discussed phthalates, those near-ubiquitous chemicals used in numerous consumer products, in previous articles. But in my role as a guycologist, I would also like to add that a recent study of adult males found an association between increased phthalate levels and decreased testosterone. Plastic, in most of its forms, is not your friend. When I previously wrote about BPA (also found in many plastics) I mentioned that it has been linked to human erectile dysfunction. But I thought I’d mention it here again, so that you can have all of your guycological information in one place.

And although the interrelationship between hormones and the brain is still not well understood, it is known that testosterone plays a role in fetal brain development. Its effects have been extrapolated to encompass sexual identification and gender identity, and play behavior. There are also some intriguing possibilities that too much testosterone is associated with autism spectrum conditions, and not enough testosterone in later years with Alzheimer’s disease.

Do I think our future is a grim one, full of infertility and strange diseases of the man-parts? No. We have personal choices and our government has policy choices. So what is a healthy American guy to do? The old standbys, of course: Eat organic, stay away from plastic. But also consider advocating for reform of the Toxic Substances Control Act. We need more male voices in this movement. If I can manage to talk to the men in my life about their prostate worries, you can take on an environmental battle that has been (so far) left mostly to the ladies.