I don't think you've asked the question precisely. Greenhouse gases do not impact human health and safety, or the economy. The economy does thrive on the production of greenhouse gases, such as CO2 emitted from factories, or gas to drive cars. However, these are a byproduct of economic activity, and the existence of the greenhouse gases does not impact on the economy.

It is theorized that greenhouse gases cause the planet to warm. Basic physics theory says that doubling the amount of CO2 in the atmosphere will cause the planet to warm about 1-1.5C. If the planet has negative feedbacks to moderate this warming, for example more evaporation of warmer water producing more clouds to reflect sunlight, then the impact on the environment is negligible. Others theorize that there will be positive feedback that enhances this warming and causes it to be a much more severe number like 2C,3C,4C.

I suspect the question you meant to ask is what are the impacts of actions to combat global warming.

Greenhouse gases are essential to keep Earth warm enough to support life. But too much of them will cause Earth to warm and have unpredictable results. One result that is predictable is that warming causes ice to melt. And since only some of this ice is floating on the ocean and the rest is on land, it will cause the sea level to rise, resulting in millions of people losing their homes.

The main greenhouse gas is CO2 measured in PPM parts per million.

CO2 can cause some warming and has, our Earth is warmer because of CO2 however CO2 warming effect logarithmically diminishes with concentration, what that means is if 10ppm cause 1C warming then it would take 20ppm to cause another 1C and then 40ppm for another and so on, at 400ppm which we have now, CO2 has pretty much done all the warming it can do.

CO2 is plant food it has been estimated that increasing CO2 has caused up to 14% more plant biomass, including better crop yields.

Very few studies have been carried out on CO2 and the economy, and most are based on CO2 warming (which at present is not happening) but most experts agree it would be beneficial only if temperatures do not exceed 2C

CO2 is a natural substance which our bodies produce, it is not toxic, but can cause suffocation at high concentrations, however submariners are allowed to work in concentrations of CO2 up to the level of 5000ppm, so it is not a health hazard.

The most significant greenhouse gas in our world is water vapor. Next the EPA will label clouds a pollutant like CO2. Not CO2 or any other gas. CO2 is so insignificant in our atmosphere and the human contribution to it is just 15 parts per million. Think 15 grains of sand out of 1 million. That's supposed to cause the world to burn up.

CO2 is a trace gas (0.04% of the atmosphere). It was once thought that CO2 increases from human emissions were causing the Planet to warm profusely and was causing a "runaway warming effect". This is an extremely flawed concept but politicians got involved and caused a panic.

Here's the reason why CO2 can not cause a "runaway effect" on or 'control' temperatures : http://tallbloke.files.wordpress.com/201...

Genetically modifying food has become a problem. Bill Gates and Monsanto (Gates invested $27 million) seem to be trying to end world hunger by modifying food products which is a dangerous proposition simply due to nutrient depletion in the food product itself and it is all in the name of profit. Thanks Bill! : http://www.opednews.com/articles/Bill-Ga...

http://truthfarmer.com/2013/09/26/monsan...

GHG's benefits are that they keep the earth warm enough to live on. Without them, it would be much to cold to survive.

GHG's risks are that they pollute our atmosphere and water. Due to humans polluting Earth, they are now warming up the globes average temperature and melting ice around the world. Which in turn only warms up the earth even faster. They can hurt humans with polluted drinking water and the air that we breath. Once oil, coal, natural gas etc run out. The economy will likely go to ****, as we are over invested in these industries.

Your answers are here.

Top climate scientists say there is no man-made Global Warming.

The Great Global Warming Swindle