Table 2.

Environmental cytotoxic agents and their antagonizing principles.

Cytotoxic Agent	Mode of Cytotoxic Action	Antagonizing Principles	Remarks
Singlet oxygen (1O2)	DNA damage, especially guanine [21,22]	Carotenoids [23,24,25]	Skin and eye exposure
Ozone	Formation of ozonides and cytotoxic aldehydes [26]	Ascorbate, GSH, urate [27,28]	Exposure to respiratory system [29,30]
Sunlight	Induction of photooxidative processes, formation of 1O2 [31]	Melanin, polyphenols, [32]	Skin exposure
Ionizing irradiation	Water radiolysis, formation of solvated electrons, O2•−, H2O2, •OH, and substrate radicals [33,34,35]	See remarks in Table 1	Always present at very low level