airplane—led to the geopolitical importance of petroleum resources. The Middle East, home to many of the world's oil deposits, became a center of geopolitical and military tension throughout the latter half of the century. (For example, oil was a factor in Japan's decision to go to war against the United States in 1941, and the oil cartel, OPEC, used an oil embargo of sorts in the wake of the Yom Kippur War in the 1970s). The increase in fossil fuel consumption also fueled a major scientific controversy over its effect on air pollution, global warming, and global climate change. Pesticides, herbicides and other toxic chemicals accumulated in the environment, including in the bodies of humans and other animals. Population growth and worldwide deforestation diminished the quality of the environment. In the last third of the century, concern about humankind's impact on the Earth's environment made environmentalism popular. In many countries, especially in Europe, the movement was channeled into politics through Green parties. Increasing awareness of global warming began in the 1980s, commencing decades of social and political debate. Engineering and technology One of the prominent traits of the 20th century was the dramatic growth of technology. Organized research and practice of science led to advancement in the fields of communication, electronics, engineering, travel, medicine, and war. Basic home appliances including washing machines, clothes dryers, furnaces, exercise machines, dishwashers, refrigerators, freezers, electric stoves and vacuum cleaners became popular from the 1920s through the 1950s. Radios were popularized as a form of entertainment during the 1920s, followed by television during the 1950s. The first airplane, the Wright Flyer, was flown in 1903. With the engineering of the faster jet engine in the 1940s, mass air travel became commercially viable. The assembly line made mass production of the automobile viable. By the end of the 20th century, billions of people had automobiles for personal transportation. The combination of the automobile, motor boats and air travel allowed for unprecedented personal mobility. In western nations, motor vehicle accidents became the greatest cause of death for young people. However, expansion of divided highways reduced the death rate. The triode tube was invented. Air conditioning of buildings became common New materials, most notably stainless steel, Velcro, silicone, teflon, and plastics such as polystyrene, PVC, polyethylene, and nylon came into widespread use for many various applications. These materials typically have tremendous performance gains in strength, temperature, chemical resistance,