There are more than 8 billion people in the world, and each one passes gas about 13 to 21 times a day, emissions that are mostly odor-free, containing nitrogen, oxygen, hydrogen, carbon dioxide, and methane — but sometimes with smelly hydrogen sulfide.

That's one form of natural gas.

The other is the natural gas that may power your stove, furnace, or water heater. According to a study from Harvard’s T. H. Chan School of Public Health, if it leaks out it will deliver varying levels of chemicals that are toxic, linked to cancer, and can help form ozone and particulate matter.

The researchers found 21 federally designated hazardous air pollutants in the 296 samples they took from people’s homes in the Boston area.

What does this mean for people who love their gas stoves?

You can opt for electric. These days the burners are more responsive to temperature changes, and convection ovens are a great new tool.

But if you are sticking with gas, here's what the researchers suggest:

• Have an in-home natural gas leak detection survey conducted by a professional to check that no small leaks are present. This check is more sensitive than the methane detector you should have in the kitchen and near your furnace.

• In the kitchen, open windows and run an over-the-stove vent that sends exhaust outside.