There are two types of ingredients in shampoo. One type cleans your hair. The other type strokes your emotions. I’m holding a bottle of Pantene Pro V, one of the world’s most popular shampoos. Of the 22 ingredients in this bottle of shampoo, three clean hair. The rest are in the bottle not for the hair, but for the psychology of the person using the shampoo. At least two-thirds of this bottle, by volume, was put there just to make me feel good.

The world spends around $230 billion on beauty products every year. Of this figure, $40 billion go to shampoo purchases. North Americans blow almost $11 billion on shampoo and conditioner each year. So most soap manufacturers aren’t willing to rely on a product that merely works. The bigger job is convincing the consumer that their soap is adding value to the consumer’s life. So shampoo bottles include extra concoctions aimed at convincing the man or woman in the shower that the soap is more “luxurious” or “effective.” Because beautiful hair doesn’t just happen.

Have you got the greasies? One shampoo ingredient is all you need: detergent. Detergents are chemicals designed to bond to both water and grease. When the shampooer massages shampoo into the scalp, the detergent adheres to the grease. The detergent attaches to the rinse water and leaves, taking the grease (sebum) with it.

The most common shampoo detergents are ammonium lauryl sulphate and one of its molecular sidekicks, ammonium laureth sulphate. These viscous, yellow liquids, with the water of a shower, are enough to make your hair clean. They help stop the greasies.

Shampoo tends to use five factors to help the user feel good about it: shine, thickeners, lather, color, smell, coatings and exotic ingredients. Those ingredients, though they have nothing to do with cleansing, are part of the sell to convince you that something beautiful happens to your hair.

Consumers value shininess in nearly everything, including hair. For hair to shine, the cuticles of the hair must lie flat. Imagine a strand of hair as a stack of flimsy paper cups. When all the lips of the cup, called imbrications, lie flat, hair shines. Dull hair has the cups’ lips sticking up. To get imbrications to lie flat, hair needs to be exposed to mildly acidic substances, so substances like citric acid are added to make the imbrications lie down and give hair that shiny look and to let yourself glow.

Consumers believe that thick is better. Which may explain why George Bush was a two-termer. Shampooers trust the velvet heft of the shampoo in the palms of their hands. So five of the 20 ingredients on the list are there because they help thicken the soap. Thickness also guarantees that people use more shampoo than necessary. There’s salt, glycol distearate, cetyl alcohol, ammonium xylene sulfonate and others: body on tap.

And where would we be without suds? Cleaning agents do tend to foam a little when they’re used, but the bubbles don’t affect the cleansing much. However, the extra lather helps convince the shampooer that the soap is working. Lathering agents are added to boost the suds, chemicals like cocamide MEA. This little devil, besides being toxic in a few ways, also helps the lather to stay once it’s been raised, a sudsy Viagra, with the help of known associates like the plastic PEG-7M. Great lather for great-looking hair.

Consumers tend to believe that good things must also be pretty. So shampoo manufacturers add colors, like purple and green, with reflective particulates to form blossoming clouds. Colors are often a problem either for humans or for the environment, like good old red dye no. 3, banned in 1990, eight years after a number of reliable studies revealed its cancer-causing tendency. Don’t hate it for being beautiful.

Smell is important, because after the bathers have washed their hair, smell reminds them that the soap has done its job. Gee, some hair smells terrific. Smell is often associated with a brand, and smell helps to form the most intimate psychological connection a soap can make with its user. But the more “natural” the smell, the less natural the machinations behind it. That lovely apple smell has about as much to do with apples as Dick Cheney with world peace. And fragrance can be particularly dangerous because it’s not specifically labeled. It’s a combination of ingredients that could be harmless, on one hand or, on the other, noxious.

Once the natural oils have been removed from scalp and hair, shampoo often replaces them with conditioners derived from animals or plants. These conditioners coat the air and smooth its surface. The bottle of shampoo I’m holding uses dimethicone to coat the hair (it also helps to thicken the shampoo). It’s a silicone-based chemical that coats hair and skin. You’ll also find it in caulking, Silly Putty, and herbicides. No more tears. No more tangles.

Some shampoo sounds more like chicken marinade than shampoo, boasting of vitamins, minerals, protein and herbs. But, the vitamins and minerals and exotic extras play a useless role. So whether the shampoo brags that it is “infused” with real beer, exotic proteins, vitamins, antioxidants, or extracts from some fabulously endangered species, the additive saturates the users’ minds, not their hair.

All these ingredients would go bad were it not for preservatives, a chemical equivalent of the right to bear arms. Sodium benzoate, for example, is handy because it kills nearly every living thing that might start to grow in a shampoo bottle. Ironically, in most cases the detergents won’t go bad. It’s the psychological ingredients that need preservation.

And these chemicals are tough to track down because tracking chemical names, it turns out, is a little like tracking criminals. Most have several aliases and fake IDs, play a role in many different products, and are shifty when caught and questioned. Some have long toxicity records; others are suspects in a range of problems. Of the 22 shampoo ingredients in my hand, all except three have proved to contribute, or are suspected of contributing, to health or environmental problems. Most of these ingredients, though known toxins, are permitted for use, because the small quantities limit human and environmental exposure.

Most of the ingredients in shampoo “may” cause health concerns. The word “may” is used because most chemicals have never been tested. Of the more than 80,000 chemicals registered and used in the U.S. since World War II, fewer than 500 have ever been properly studied for their effects on humans and the environment. So it’s hard to say exactly how dangerous it is to use shampoo every day.

In May, 2008, Jane Houlihan, director of research for the Environmental Working Group, reported on the dangers of cosmetics and personal care products to a House subcommittee. She believes that these products, including shampoo, are the biggest source of human exposure to dangerous chemicals. According to Houlihan, “companies are free to use almost any ingredient they choose in personal care products, with no proof of safety required.” Consumers are not properly warned of possible dangers because of a “lack of standards and labeling loopholes.” Let’s just say that the less you hang out with any of these chemicals, the better off you are, we all are.

Mount Sinai Hospital reports that 2.5 billion pounds of toxic chemicals are released in the U.S. each year, the equivalent of 37,100 tanker trucks of noxious chemicals. A lot of these chemicals are released from homes every day. Daily, 45 billion gallons of wastewater go down the drain to be treated at one of the 16,000 water treatment plants in the U.S. But wastewater plants are designed to handle only the major pollutants. They can’t remove the diversity of chemicals that humans flush every day.

This is the big problem with the shampoo ingredients: When a man rinses his hair, all the ingredients wash down the drain, carrying the grease to boot. And as one man’s shampoo travels down the pipe, it meets up with a woman’s, and so on, and so on, and so on. At least 350 million gallons of shampoo and its unregulated ingredients flow down U.S. drains every year. And many of these chemicals flow straight into our freshwater systems.

Shampoo, for example, contributes to high levels of estrogen and estrogen-like substances (endocrine disrupters) in freshwater downstream of sewage treatment plants that damage fish populations and cause male fish to grow ovaries, a sort of liquid feminism. My hometown of Calgary, Canada, studied the fish downstream of where we add our treated sewage to the river and discovered that female fish outnumber male fish 9 to 1. Estrogen runs through it. One study identifies more than 200 chemicals that are still present in wastewater after treatment. But the problem is likely much larger: environmental damage is difficult to estimate because we’re dumping chemicals into the environment that have never been studied.

As we get to know some of these chemicals better, we discover that they should not be trusted. Health Canada is proposing concentration limits for two common shampoo ingredients, siloxanes D4 and D5, aka, Octamethylcyclotetrasiloxane and Decamethylcyclopentasiloxane, respectively. D4 and D5 did make hair easier to dry, silky soft, and easier to work with. Also handy when making plastics and paint. Sometimes you need a little D4 or D5. Sometimes you need a lot. But Health Canada suspects that D4 and D5 are affecting fish and aquatic organisms. But, oh, how hair shines.

So I can live without the bottled psychology. My new shampoo, Sunlight Dish Detergent, has just four ingredients. It’s runny and slightly acidic, smells vaguely lemony, doesn’t foam excessively and looks anemic. It’s not perfect, just better. I need to apply it only once when I shampoo. With each shampoo, I use a 10th of the volume that regular shampoo requires. The bottle will last at least a year, as my last one did. And though its ingredients aren’t worth celebrity endorsement, my hair gets clean and I expose my body and the environment to less risk.

There is only one way humans are made to move. They are made to walk. There are many other ways to get around. You can canoe, for instance. Or paraglide. Or jog. But these modes of transportation are not the staple of human mobility. Walking is unavoidable, a necessity for those with two working legs.

The entire scheme of nature, and the human’s place within it, is built around the understanding that humans use their legs to move. It’s a great unspoken assumption. The earth expects humans to walk.