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In principle, individuals with access to high-quality tap or spring water should avoid drinking rainwater.
Collecting rainwater only makes sense if you have a country house, as rainwater is suitable for bathing and watering plants.
Why people should not drink rainwater
Tap water contains more impurities than rainwater. Drinking water should not be excessively pure, contrary to what one may expect.
Rainwater is poor in minerals
Minerals and organic substances present in bodies of water such as seas, rivers, and lakes transform into rain when water evaporates due to the sun’s heat. As water heats up, it converts into steam, and initially, the steam is solely composed of pure water molecules because most dissolved substances in water require higher temperatures to turn into steam.
Streams of warm air and vapor rise into the troposphere, the lower layer of the atmosphere. The water molecules, which move chaotically, lose energy and slow down due to the coldness of the troposphere. At this point, cloud condensation nuclei attract the water molecules.
These are tiny particles smaller than a micrometer that are lifted into the air by dust storms and volcanic emissions, crystals of mineral salts that enter the air along with sea spray, or mineral and organic acids formed during the combustion of forests or organic fuels.
Water molecules gather into a drop as they are attracted to the condensation nuclei. Once the drops reach a sufficient size, rain begins. However, since the condensation nuclei are tiny, the resulting rainwater contains few pollutants and nutrients.
For example, rainwater does not exceed a concentration of 0.9 mg/L of calcium and 0.08 mg/L of magnesium, while tap water contains tens of times more.
Drinking mineral-poor water ultimately reduces the intake of calcium and magnesium, which are crucial for bone and cardiovascular health. Rainwater, on the other hand, does not pose any significant health risks.
Rainwater can contain pathogens and chemical pollutants.
Rain that falls over a forest or rural area keeps the water relatively clean as it reaches the ground.
Hence, small snack bar and cafe owners in remote regions, far from cities and industrial plants, can boil rainwater for making tea or coffee.
Experts do not recommend drinking non-boiled rainwater, even in rural areas where it is collected in barrels standing on roofs or on the ground. Open containers can allow pathogenic viruses or microbes to enter, such as when leaves or bird droppings mix in.
In the city, rainwater is even worse due to the persistent presence of aerosol particles, which form during fuel combustion and come from the exhaust gases of cars. These include toxic organic compounds, nitrogen and sulfur oxides, and soot, all of which contribute to the contamination of the air.
Aerosol particles from the atmosphere are drawn towards raindrops, causing dozens, and at times hundreds, to accumulate on their surface. This results in rainwater being contaminated with harmful organic compounds and soot.
City rain becomes dirtier as its drops decrease. Water closer to the earth’s surface contains aerosols, heavy metals, asbestos, and harmful microorganisms from bird and rodent droppings, which enter the water from roofs and drains.
Boiling water alone is insufficient since it does not eliminate organic and inorganic impurities. Filtering urban rainwater is necessary for purification. Pitcher filters lower pesticide and certain harmful organic compound levels, but fail to decrease nitrates and lead content.
Complex water treatment systems, such as ion exchange resin filters or reverse osmosis filters, are necessary to purify harmful impurities from city rainwater. This becomes an unjustifiable challenge in situations where access to tap water is available due to its high cost and difficulty.
How can rainwater be used?
Some international organizations’ representatives recommend that people living outside the city should collect and use rainwater for technical needs.
Rainwater is good for washing and bathing
Water contains very little salt, making it easy to remove soap and shampoo while causing the scalp to dry out less. People with dry skin and atopic dermatitis can benefit from washing in low-salt water.
Rainwater is optimal for watering plants
Nitrogen oxides saturate water droplets in the air. Chlorophyll, the main plant protein, is synthesized with the help of nitrogen dissolved in water. Therefore, rainwater from the countryside is the optimal watering solution for indoor and garden plants.
It’s crucial to keep in mind that rural rainwater surpasses urban rainwater significantly in quality. Sulfur and nitrogen oxides dissolve into water droplets during precipitation in the city, causing the water to transform from a neutral to a mildly acidic state. These precipitation instances are widely known as acid rains.
Slightly acidic rain doesn’t harm a person on a walk, but it isn’t suitable for watering houseplants since it washes out the minerals and nutrients plants need to grow from the soil. Thus, only plants that are tolerant to acidic water can use rainwater collected in the city for watering.
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