Disadvantages of In-Office Whitening. 1  In-office bleaching is more expensive than take-home alternatives. 2  Its cost, on average, is $650, compared to $400 for take-home trays and under $100 for over-the-counter bleaching trays or whitening strips.
Planetary protection is a guiding principle in the design of an interplanetary mission, aiming to prevent biological contamination of both the target celestial body and the Earth in the case of sample-return missions.
Ozone Layer Protection. Welcome to EPA's ozone layer protection web area. The ozone layer is Earthâs âsunscreenâ â protecting living things from too much ultraviolet radiation. The emission of ozone depleting substances has been damaging the ozone layer. But through domestic and international action, the ozone layer is healing and should fully recover by about 2065.