Fluorine

The most chemically reactive of all known elements is fluorine – a pale yellow, corrosive gas. Due to its high reactivity, this member of the halogen group is always found as a fluoride in minerals. Its irritating odour leads to the ready detection of toxic fluorine gas.

Well-known are high temperature plastics made of fluorine and carbon – called Teflon^TM – that coat pots and pans, producing non-sticky cooking surfaces. In the past, fluorine derivatives known as chlorofluorocarbons (CFCs) were used in aerosol products. Since these CFCs adversely affect the Earth's ozone layer, they have largely been replaced by hydro chlorofluorocarbons (HCFC), which are used extensively in air conditioning and refrigeration. By 2020, the use of HCFC will be phased out (99.5%) in Canada.

The toxic nature of fluorine poses serious consequences to human health. At high concentrations, this gas is not only an eye irritant, but also asphyxiates, causing lung congestion. It is also corrosive and skin contact results in severe thermal burns. Although the metal fluorides of this halogen are extremely hazardous, its organic fluorides are usually quite harmless.

Despite its toxicity, fluorine is is generally regarded as beneficial to mammals, including humans.