The internet is a very difficult thing. It's extremely hard to ever find out what you are looking for.
I am wondering what isobutane does to the environment, what it does to people, and why they put it in hairspray. I am also wondering those same questions for copolymer (nail polish) and dimethicone (eye shadow).
If anyone knows a good site to find these answers to, or knows any of this, it would be great if you could respond asap.
Thanks!

http://www.cosmeticscop.com/learn/dictionary.asp?TYPE=SEARCH&ID=D

Has link for dimethicone and may have for the others.

I'm a chemist who once worked on ink formulations. Not the same thing, but some similar applications.

The isobutane is likely the propellant gas in hair spray.

The copolymer in nailpolish is likely an acrylate or other polymer used when making the nail polish. Nail polish is likely a mix of colorant(s), polymers, solvents, and other additives. The solvent makes everything wet for application and then evaporates quickly when applied. The additives help stabilize the solution so, for example, the colorant stays mostly mixed up. The colorant, well, gives the color you want. The polymer gives the thing the properties you want. Such as shiny, hard, durable... some polymers can give a product that is flat, some are glossy. Some are tacky or sticky, some are not. So the polymer will be a main source for all the properties you want in a polish, like sticking to nails and not coming off easily, or gloss, or durability... as well as also "holding" the colorant also... you wouldn't want the color from your polish to rub off on your clothes, face, etc.

Dimethicone is a silicone polymer. I've used silicone polymers as thickeners, as well as other properties like gloss, stabilization of the mixture...

As for effects... this could be tricky. If you look up the material data safety sheets (MSDS) for the chemicals it'll tell you some of the physical hazards of the chemicals. You have to be careful though, cause people freak out when reading msds sheets. The issue is that health effects depend on the route of exposure (breathing, skin, ingestion, injection... ), the concentration and amount of exposure (a drop, a gallon, a swimming pool full), and the length of exposure (one second, one minute, every day for a week, for a year... )

So the point is that you will die if you sit around in a vat of gasoline for long enough. But pumping it into you car carefully probably won't hurt you... unless your smoking and it ignites.

So search for "MSDS isobutane", look at some links... read through the msds until it tells effects. Just understand that about everything can hurt you. Eat a bunch of salt and your heart could stop. Give a newborn too much ulta pure water and their kidneys fail. Inhale dirt and you can suffocate.

So effects on msds need to be considered carefully.

Also, you might find your librarian can help you with searches like this. Science searches on the internet sometimes can be ugly. Sometimes the library will have more difect answers through the searchable cd databases.