Thats alot of questions.

1. The history of air conditioning goes back to the Romans. They would circulate cool water through walls of a building to keep the brickwork cool.

2. The ancient Chinese used hydraulic fans to chill out.

3. In medieval Persia they design window towers which sucked out warm air and pulled down cool air.

http://inlinethumb64.webshots.com/42687/2180334850104181437S600x600Q85.jpg

I think the positive side of air conditioning is pretty well known. It keeps you cool on sweltering hot days and can save the lives of the elderly during heat waves.

The negative side of air conditioning include building related illness (BRIs) such as breathing difficulties, skin irritations, headaches and tiredness.

Prolonged exposer to a malfunctioning AC unit can also lead to hearing loss.

The major difference between air conditioning in a car and an office building is that you are sharing a building with so many more people and germs which might be a concern.

http://www.norcalblogs.com/sustainable/fan.gif

hi! Air conditioning can be good for your health for these reasons
1. keeps the air dry, prevents bacterial and virus growth. This is what hospitals do
2. can have a pollen filter installed, cutting down on allergies (change the filter frequently)
3. can keep the temperatures moderate, thus not making people (and pets) uncomfortable

Air conditioning can be bad for health
1. if the ducts are not kept clean
such as mold growing in them
http://www.doh.state.fl.us/environment/community/indoor-air/mold.htm
or too much dust
They should be professionally cleaned once a year by a furnace expert

Car air conditioning follows most of the same principles, regarding comfort, safety of driving and mold.

They should be used once or twice a month year round, just to keep the air flow going. They should be used frequently in hot months. They should be inspected by professional auto service people, if they smell moldy, dusty, or are not functioning right.

Just like everything in life, AC versus no AC is a give and take thing. Sweating is a normal human body function that cleans your pores and helps rid your body of toxins. If you don't ever sweat, it can cause a build up of toxins in the body. I have also heard that constantly switching from cold AC to really hot weather outside, like if you are constantly leaving and house and walking back inside, takes a toll on your immune system and can cause illness. Also, constantly keeping the air conditioning on and never opening your windows can cause allergens and bacteria and all sorts of horrible things to build up in your home. You should shut off your AC and open all the windows in your house at least once per week to get a good exchange of air, since AC units typically do not take fresh air from outside, but recycle the air that is already inside. This also replaces lost oxygen in the air from constantly rebreathing the same air over and over again.

On the other hand, air conditioners have built in filters that, when changed regularly, can help with allergens. Of course not all AC units are up to par on this.

One thing I have noticed is all the people I know of who keep their AC units extremely cold have weight problems. I have a theory myself that when the body is kept too cold on a constant basis, it tends to put on weight as insulation.

Before AC was invented, people just dealt with it and sweated a lot. Of course there were little techniques to make it not so bad, like placing a fan behind a shallow pan of ice water as a primitive form of air conditioning. People also planned the building of their homes a little better. Adobe homes, found mainly in dry hot regions, have temps inside that are an average of 10 degrees cooler than outside temps. Also, subterranean homes, especially those where the roof is not exposed, stay at a constant 76 degrees, negating the need for AC at all. Even so, people did still suffer with the heat and, as a consequence to constantly sweating, had to take salt pills and drink plenty of water to replenish what was lost due to the constant sweating they endured.

Overall, I feel air conditioning is a good thing for the elderly or those suffering with health problems, but us healthy adults need to learn to either turn up the thermostat a little or turn it off completely and open the house up once in awhile for many different reasons, including saving money and energy, and to get a good exchange of air and to allow our bodies to sweat a little. How spoiled we are to expect the temperature in our homes to be at a constantly perfect level?