The second is the production of particulate matter and exhaust gases. Prodigious amounts of poisonous gases and particulate matter pour from the smokestacks of the cities' innumerable factories, from the throngs of automobiles crowding their streets, and from the swarms of jets in the skies (and even a little from all the cigarettes; I will answer later to the charge that we have cigarettes and cars in the country, too). Not only does all this pollute the atmosphere, it is also said that the particulate matter blocks the light of the sun, thus causing a drop in the temperature on the Earth. There is no reason to believe that this will be balanced off satisfactorily by the greenhouse effect. The increase in carbon dioxide, poisonous gases, and particulate matter in the atmosphere threatens the lives of all living things on our Earth. 3. Depletion of the Ozone Layer The third is the depletion of the stratospheric ozone layer. Those ever-so-convenient city inventions the jet plane and the aerosol spray, and the nitrogen fertilizer that the city invented to dominate the farming villages, are the instruments by which the city is destroying the ozone layer. The effects of the exhaust gases and nitrogen oxides released in the stratosphere by jet planes will, in the final estimation, reduce the ozone by 6.5 percent. And it is thought that the CFCs used in aerosol sprays, which rise to high altitudes upon their release, will, even if their use continues at the 1974 rate, cause a 14 percent loss of the ozone over the next 50 years. The nitrogen suboxide released when the nitrogen fixed in chemical nitrogen fertilizers is denitrified will, it is estimated, cause a future 3.5 percent reduction of ozone. A 1 percent reduction in ozone translates to a 2 percent increase in ultraviolet radiation reaching the Earth's surface, and an increase in ultraviolet radiation is a threat to all living things on Earth; it is said that, if nothing is done about this -- if the ozone layer continues to be destroyed -- certain species will be faced with extinction. Since all species in their interactions work to maintain the ecosystem, the loss of even one could signify grave consequences for the ecosystem as a whole. As for human beings, should there be a 10 percent reduction in ozone, it is thought that cases of skin cancer could increase 20 to 30 percent. The cities steal nitrogen and oxygen from the atmosphere, they rob metals and petroleum from the earth, and their wonderful scientific achievement is to put us and the entire ecosystem in mortal danger by means of the production and use of their inventions. 4. Sewage Fourth is the dumping of sewage into the ocean. In order to maintain convenience, extravagance, and ease, the city must somehow dispose of the great amounts of water it converts into sewage, and that sewage always ends up in the ocean. The amount of sewage produced is about equal to the amount of water consumed.