The nitrogen oxide given off by exhaust mixes with moisture in the air to form nitric acid, it then returns to the Earth as acid rain. Cars account for about half of all nitrogen oxides produced in the US. How long has this been a prevalent problem? .
The term acid rain was first considered to be important about 20 years ago when scientists in Sweden and Norway first believed that acidic rain may be causing great ecological damage to the planet (Forster). The problem was that by the time scientists found the problem it was already very large. A lake does not become acidic over night. It happens over a period of many years, some times decades. How could we let it get to this point? Acid rain does not kill trees immediately or directly. Instead, it is more likely to weaken the tree by destroying its leaves, thus limiting the nutrients available to it, making it susceptible to extremes of heat or cold and also to insects such as the gypsy moth, and other environmental stresses. Or, acid rain can seep into the ground, poisoning the trees with toxic substances that are slowly being absorbed through the roots. Many people wonder how the amount of acid is measured? .
Acidity is measured on what is known as the pH scale. Fourteen is the most basic, seven is the most neutral, and zero is the most acidic. Normal rain is slightly acidic with a pH level around 6.3 due to the natural atmosphere and rain less than 5.7 is considered 'acid rain' (Elliott). When acid levels in lakes reach levels around 5.6 fish cannot reproduce any longer and eventually die off of suffocation. Because toxic materials such as mercury are deposited in the fish due to acid rain, it is dangerous for humans to consume the fish in these lakes. Like the domino effect, fewer fish can be sold as food, fishermen lose their hobby and people selling fishing supplies are even affected. Why would we let such a problem continue to bring down such a lucrative trade? In just ten years Lumsden lake in Ontario, Canada went from a pH reading of 6.
