Question! How to choose a quality candle

There's something so attractive about burning candles - perhaps it appeals to our genetic memory, our fascination with fire and is a reminder of simpler times. The Egyptians and Cretans made candles from beeswax, as long as 5,000 years ago.

Paraffin wax - not so green
Most cheap candles you buy at the supermarket are made from paraffin wax, which is a byproduct of oil refining. Even the wicks of some candles can cause problems - they may have a lead or other type of metal core that release toxic emissions during burning.
Paraffin wax consists of alkane hydrocarbons and melts between 47°C and 65°C (around 120° to 150° F). It is derived from light lubricating oil distillates. When burned, the fumes can contain a number of carcinogens including Acetaldehyde, Acrolein, Benzene, Formaldehyde, Polychlorodibenzo-p-dioxins, Polyaromatic Hydrocarbons and Toulene.
As the carbon within paraffin wax was was originally deep underground in oil deposits, when they are burned the carbon they contain is released into the atmosphere, adding just a little bit more to the already high levels present.
Unfortunately, by using paraffin based candles, we are helping to support the environmentally destructive oil industry and further poisoning our air.

Lead/metal wicks
The lead core wick issue shouldn't be such a problem in the USA and Australia now, but I'm not sure about other countries.
In the USA, voluntary agreements between manufacturers not to use lead cores were in place since the 1970's. Unfortunately, some cheap imports continued to contain lead wicks. In 2003, the U.S. Consumer Product Safety Commission (CPSC) formally banned the import, manufacture and sale of candles with lead-cored wicks. Australia banned candles with lead core wicks in 1999.
The problem is most of us stash away candles for emergencies and they can go unused for many years, so there's still probably millions of lead core wick candles laying around the place.
Some lead core wick candles emit lead levels in excess of 3,000 micrograms per hour - about seven times the rate considered unsafe. Lead is a cumulative poison and never leaves the body - a dose here and and dose there can build up. It not only affects humans, but all animals and can be passed along the food chain.
If you have old candles, inspect the wick and look for a thin wire in the center. Separate the core from the wrapping if need be to be sure. If there is a wire, there is a possibility it's not lead as some manufacturers now use zinc or tin instead; but there's some debate as to the safety of these elements too. There's also the damage that the mining industry wreaks on the environment to consider.
On top of all this are some of the synthetic chemicals that are used in scented candles which can also give off environmentally damaging emissions.

Earth friendly candles
Perhaps it's 'extreme green' to concern ourselves with such seemingly small things, but all of us can make minor adjustments in our lifestyles to have less impact on our environment. For one person, it might be to cut down driving, for someone else it might be purchasing candles that are more earth friendly. Every small change makes a difference if it's multiplied millions of times.
There are many alternatives to paraffin wax candles, but it's important to note that the burning of just about any substance will create some sort of emission, and even "green" substances can be toxic.
For example, never burn oleander as the smoke is definitely toxic and can kill you - but I doubt very much you'll ever see oleander candles for sale. I guess what I'm trying to say is be careful of outlandish claims of greenness in any products - the key is all things in moderation. Many alternative wax candles may also contain some paraffin to assist with burning.
Of the alternative waxes available on the market, soy wax or bees wax candles are probably the most popular. Both these substance have a lower melting point; so if you live in an area where it's extremely hot, try and store them in a cool place or at least lay them flat in storage to prevent them from wilting. In my shed in the outback, I saw even the paraffin candles I had in candleholders winding up looking like soggy celery after a hot day!
Usually if you buy scented beeswax or soy candles, the scent will be from natural oils rather than synthetic chemicals, but it's always wise to check to make sure. The same goes for the wick - it should be made of recycled cotton, hemp or recycled paper fiber.