The idea of tilting your head back and catching raindrops on your tongue feels primal and pure. But is drinking rainwater as it falls actually safe. The answer depends heavily on where
To make rainwater safe, it must be properly treated, tested, and stored. The Centers for Disease Control and Prevention (CDC) recommends filtering and disinfecting rainwater for drinking purposes. You are, what’s in the air above you, and how much you’re drinking.
Is It Safe to Drink Rain Water
No, it is not safe to drink rainwater directly because it can contain harmful bacteria, pollutants, and chemicals. While rainwater is essentially distilled water high in the atmosphere, it collects contaminants as it falls and as it is collected. To make collected rainwater safe for consumption, you must use proper filtration and disinfection methods.
- Airborne pollutants: As rain falls through the atmosphere, it acts as a sponge, absorbing gases like sulfur dioxide and nitrogen oxides, which cause acid rain in polluted areas. It also picks up dust, soot, and microscopic particles, including “forever chemicals” (PFAS) that have been found in rainwater worldwide.
- Contamination from collection surfaces: Most rainwater is collected from roofs, which can be covered in bird droppings, animal feces, dead insects, leaves, and other debris. The materials of the roof, gutters, and piping can also leach chemicals and heavy metals such as lead and copper into the water.
- Poorly maintained storage tanks: Water stored in tanks can become a breeding ground for microorganisms like bacteria, parasites, and viruses. If not properly sealed, tanks can also allow entry to insects and rodents.
Even after treatment, certain individuals are at higher risk of getting sick from waterborne germs and chemicals. The CDC recommends that infants, young children, pregnant women, the elderly, and people with compromised immune systems avoid drinking rainwater entirely.
What Are The Benefits of Drinking Rainwater
Just plain rain water in the air is distilled water H2O, but as soon as those drops start falling, they’re going to collect whatever’s in the air around them.
Imagine that every single raindrop is a little paralysed sponge. Down here, it also becomes impregnated with gases, snags particles and scoops up floating microorganisms in its descent. Once it hits the ground, that “pure” water is a solution of everything on which it rained.
The collection process isn’t selective. “All dust, harmless or hazardous, rainwater treats the same. Anything wafting through the air around you will become part of what you’d be drinking.
Geographic Reality Check
You tell more about what’s in your rainwater by the place where you live than anything else.
The clearest rain falls in remote wilderness areas. Remote places, isolated from roads, factories and farms also imply fewer pollutants in the air. It includes mountainous or heavily-forested areas, and other places remote from human habitations. The air is cleaner, and so the rain remains comparably clean.
It is the reverse in an urban atmosphere. Cities are where you get a concentration of pollution from cars, industry and everything else the millions of people who live there do every day. When rainwater descends through urban air, it gathers up all sorts of nasties – exhaust particulates, industrial emissions and urban dust. The greater the density of contamination sources, the more contaminated it will be.
Agrarian areas have their own problems. Those can all become airborne: pesticide drift, fertilizer dust, and emissions from farming equipment. Rainwater in these areas might have agricultural chemicals from nearby use that was not actually sprayed on your property.
Coastal areas contribute salty spray to the smoggy cocktail, although that’s typically only noticeable very close to the ocean. Coastal areas more often are troubled by industrial port activity and shipping emissions.
The Impact of Air Pollutants on Rainfall
Four hundred ppm of carbon dioxide is going to change atmospheric chemistry to the extent that humans will be interacting with a chemical environment in the air unlike anything their species has ever encountered. Human industry has significantly altered the composition of the air in countless inhabited regions.
Particulate matter comprises small solid or liquid particles suspended in the air soot from burning fuel, dust from construction and destruction, tire-wear particles and industrial emissions are common examples. These particles easily “grab” water droplets while falling.
A gaseous pollutant dissolves in rain directly. Acid rain is the result of sulfur dioxides and nitrogen oxides, which cause acidic conditions. Carbon monoxide, ozone and volatile organic compounds all begin mingling with the chemistry of falling water.
Airborne heavy metals, including lead, mercury and cadmium are present in the vicinity of industrial zones and high volume traffic roads. These accumulate in biological systems and it is repeated exposure that should worry us rather than a single incident.
Today, microplastics are found in rainfall even in far-flung places. These tiny plastic particles spread around the world on air currents and fall out of the skies with rain.
The “first rain” phenomenon only worsens matters. The atmosphere gets laden with pollutants when there is less rain over the course of dry years. The first rain of a storm is basically an air-quality scrub good for the atmosphere, bad for anyone drinking that initial flush.
the Biological Pollutants of Water Pollution
Rainwater isn’t sterile. The air hosts living microorganisms that can settle on clouds, where they feed and reproduce.
Because bacteria hang a ride on dust and in water droplets in clouds. Most atmospheric bacteria are non-pathogenic species of environmental origin, however pathogens can also be brought into the air by soil disturbance, waste-water treatment plants and animal production.
When airborne, viruses can stay aloft for hours and even longer when present in aerosol form. Dilution and exposure to U.V. light will lower the presence of viruses in rainwater, but it’s not zero risk.
2.3 Fungal spores in the atmosphere Exposure of airways to fungal spores is a universal phenomenon. Most are harmless to healthy people but can cause respiratory problems or infections in susceptible individuals.
Bird and bat droppings on surfaces where rain can splash also may introduce other pathogens. That becomes more important if you’re collecting rainwater for storage, rather than simply drinking it as the water pours out of the sky.
How Pesticides Cause Air Pollution
2Rice and chemicals Rainfall composition presents a fingerprint of local industrial and agricultural influence.
Pesticides and herbicides are carried into the air as they are applied, and can travel long distances. Atrazine, glyphosate and other crop chemicals have been found in rainwater thousands of miles from where they were applied.
Industrial solvents and VOCs can also evaporate from factories, chemical storage and even products for consumers. These chemicals are easily soluble in rainwater.
The by-products of combustion from vehicles, power plants and industrial processes are polycyclic aromatic hydrocarbons and dioxins — compounds with established effects on health at some exposure levels.
And acid rain which is less problematic now than it was in previous decades because of emissions controls, but which remains a problem in heavily industrialized areas. Normal rainwater is a bit acidic, with a pH around 5.6, but pollution can make it far more so and dissolve metals from anything it touches.
Health Risk Assessment
The health implications of drinking untreated rainwater depend on exposure duration, contamination levels, and individual vulnerability.
- Acute risks involve immediate illness from pathogenic bacteria or viruses. Symptoms might include gastrointestinal distress, fever, or respiratory issues. These risks are higher in areas with poor sanitation or after floods.
- Chronic risks develop from repeated exposure to chemical contaminants. Heavy metals accumulate in organs over time. Persistent organic pollutants can disrupt endocrine function. These effects aren’t immediately noticeable but matter for long-term health.
- Vulnerable populations face elevated risks. Young children, pregnant women, elderly individuals, and those with compromised immune systems should avoid untreated rainwater entirely. Their bodies are less equipped to handle even low-level contamination.
- Dose matters tremendously. Drinking rainwater once in an emergency situation carries minimal risk for most healthy adults. Regular consumption without treatment is a different matter entirely.
When Drinking Rainwater Makes Sense
Nevertheless, there are conditions where drinking rainwater is either acceptible or essential.
Survival emergencies alter the calculus entirely. Where immediate dehydration is the only concern and there are no other options, rain water even in a contaminated state is, by far, superior. You’re going to die of thirst; you might get sick from drinking too much rainwater.
The safest conditions are in truly remote places where air quality is still good. If you hang out a few days from any road, factory or agricultural operation, the rain is going to be relatively clean. It’s not sterile yet, but the amount of contamination is reduced dramatically.
Minimal consumption reduces risk proportionally. It’s a far cry from taking a mouthful of sips while hiking compared to drinking rainwater instead of any other water source per se. Your body can generally cope with small exposures.
Rain published later in longer storms is typically cleaner merely because the rain earlier is dirtier. During the first precipitation episode, when volatile organic compounds are “washed” from the atmosphere, there is no reduction in acidity in subsequent precipitation. It’s not a guarantee of safety, but it increases the odds.
Proper Rainwater Harvesting
If you’re seriously considering rainwater as a drinking source, proper collection and treatment are non-negotiable.
- Collection surface matters immensely. Metal roofs shed water effectively and don’t harbor as much biological growth as porous materials. Avoid asphalt shingles, which can leach petroleum compounds. Never collect from roofs with lead flashing or pressure-treated wood.
- First-flush diverters automatically redirect the initial rainfall away from your storage tank. This removes the most contaminated water from your supply. The mechanism can be as simple as a tipping bucket or as sophisticated as an electronically controlled valve.
- Storage requires thought. Use food grade containers that won’t leach chemicals. Keep them covered to prevent mosquito breeding and debris entry. Opaque containers prevent algae growth. Install overflow mechanisms to prevent stagnation.
- Filtration removes particulates and improves taste. Sediment filters capture visible particles. Activated carbon filters address many chemical contaminants and chlorine taste. Ceramic filters provide mechanical barrier against bacteria.
- Disinfection kills pathogens. Boiling for one minute at sea level (three minutes above 6,500 feet) remains the most reliable method. UV sterilization systems work if properly maintained. Chemical treatments with chlorine or iodine tablets are portable options but leave residual taste.
Testing Your Water
There are, however, circumstances in which drinking water can be either acceptable or necessary.
Survival emergencies change the equation entirely. In the case of direct dehydration that’s not possible; however, if its survival water with no other alternative rainwater is much cleaner even contaminated. You will die of thirst; you may even get sick drinking too much rainwater.
The really safe situation is in the most remote places, where air quality has not deteriorated very much. Wait a few days from any road, factory or farm and the rain will be relatively clean. It’s not sterile yet, but there is a lot less contamination.
Minimal consumption reduces risk proportionally. It’s a different thing to take a mouthful of sips while walking (let alone hiking) compared to drinking rainwater in place of any other water source per se. In general, your body can handle small exposures.
Rain that falls later in long storms is generally cleaner only because the rain earlier in those storms was dirtier. There is little decrease in acidity with subsequent precipitation after the initial wet removal of volatile organic compounds from the atmosphere. It’s not foolproof, but it improves the odds.
The Legal Landscape
Rainwater collection legality varies by location. Some jurisdictions encourage it with tax incentives. Others restrict or prohibit collection based on water rights doctrines.
Western U.S. states with prior appropriation water rights have historically been more restrictive, though many have relaxed regulations in recent years. Eastern states with riparian water rights generally permit rainwater harvesting.
Even where collection is legal, using it as drinking water may trigger health department regulations. Some areas require permits for systems producing drinking water.
Final Thought
Rain that falls out of the sky is not particularly safe to drink, at least not in most contemporary settings. The romantic image of pure rainfall is from a pre-industrial era. The modern environment has too many variables you can’t control or guess at without testing. For any nonemergency use, be sure to treat rainwater before drinking it. The effort isn’t all that onerous basic filtration and boiling address most concerns. But the risk with your health makes skipping treatment not worth it. If you reside in a truly remote airshed with clear sky, your experience is different from someone who lives in an urban or industrial environment. Even so, treatment offers peace of mind as well as security. The rain from the sky isn’t what it used to be. That isn’t fear-mongering, it is environmental fact. Recognizing this doesn’t preclude the use of rainwater. It means you smartly use it, with the proper cautions for whatever your circumstances are.
References:
- Centers for Disease Control and Prevention – Rainwater Collection
- World Health Organization – Guidelines for Drinking-water Quality
- Environmental Protection Agency – National Primary Drinking Water Regulations
- American Rainwater Catchment Systems Association – Standards and Guidelines