. If pollutants keep building up in the atmosphere at present rates, only a few years into the 21st century will find the delicate layers of the atmosphere so damaged as to admit the sun's ultraviolet rays full throttle, or the atmosphere will be life. the city streets will surely be nonnegotiable without a gas mask, and every home will have to have special filtration devices to make air breathable. Without strict controls on polluters, today's inconvenience will be tomorrow's crises.