To most people, especially in Africa and South America, rain water is believed to be the purest form of water. people of these continents use rain water for different purposes ranging from drinking, washing, cooking and for spiritual cleansing. Some people go to the extent of storing this water in the season before the next raining season. This shows how they value the water from the sky.
With all the benefits derived from this water and the usefulness, they do not care about its purity. Rain water is naturally pure, no doubt about it, but it gets contaminated by the atmospheric pollution. This causes acid rain. Not limited to this alone, Industrial discharges such as boiling of coal and other fossil fuels to generate electricity which produces waste gases that contain harmful sulphur oxides (SO3 and SO2), and nitrogen oxides (NOx). When these gases combine with water and oxygen in the atmosphere, acids are formed. Therefore, instead of having water dropping, acids are dropping and this is called acid rain.
On the general knowledge of science, water acidity and alkalinity can be checked on a scale called pH. This scale has values ranging from 0 to 14. 7 is the mid-point and it is referred to as the neutral point, which a pure water is expected to have. Any value from 0 to 6.99 is acidic, and from 7.01 to 14 is alkaline. The Farther these points are to the neutral point, the stronger the acidity or alkalinity of the solution being tested.
Rain water is considered acidic once it has a pH level between 4.2 and 4.4. Most regular rain water have an average pH of 5.6 and this signifies that they are slightly acidic. This is possible due to the reaction between water and carbon dioxide in the air, and this has not been confirmed dangerous to man, animals, plants and environmental materials. Besides, most drinking water do not have pH 7 value due to the presence of dissolved nutrients in them. Drinking rain water is probably considered safe, although it is not recommended.
Other thing to look at is the surroundings where the water is collected. Collecting water in industrial areas where sulphur oxides, carbon dioxides, nitrogen oxides and smoke are produced is not safe. This is because of the resulting interaction of the gases and water.
Before drinking rain water, one must collect the water directly from the sky into a clean container, it should be collected immediately rain start, the water should be allowed to settle for at least 1 hour to allow the heavy particles it may contain to settle, the pH should be checked, and the water should be boiled and filtered. Boiling water will remove any harmful pathogens, filtering it will eliminate additional unwanted impurities, such as chemicals, dust, pollen, mold and other solid impurities.