water chemistry

Heavy Metals And Bioaccumulation: What You Need to Know

Part 1: Why Heavy Metals Accumulate in Your Food and Your Body

Bioaccumulation-Title_1024x1024.png

Picture the food web–an interconnected tangle of species, all relying on each other for energy and nutrients. Though most of what gets passed along from the tiniest microbes to humans enables us to live, a small fraction of it can be toxic. Heavy metals are natural elements that–in high doses–are poisonous to humans. They enter our bodies mainly from lower down on the food chain through a process called bioaccumulation.

What are heavy metals, and what does it mean for them to bioaccumulate? Why is heavy metals bioaccumulation dangerous for your health? We’ve got the answers–and some tips on what to do–below.

What are Heavy Metals?

Heavy metals are present in earth’s crust alongside other metals, minerals, and organic matter. Some examples include: mercury, lead, arsenic, cadmium, chromium, copper, & thallium. Heavy metals are defined as “heavy” in comparison to water, meaning that they have a higher molecular weight than 18 g/mol. Heavy metals also find their way into watersheds from concentrated wastewater, sewage, industrial activities, and mining operations. These metals can contaminate soil systems and water sources.

People are exposed to heavy metals in a few different ways, primarily through drinking water or food (crops can uptake metals from contaminated soil or meat and fish products may contain bioaccumulated metals). Many heavy metals are poisonous to humans, even in small concentrations.

What is Bioaccumulation?

Bioaccumulation is essentially the buildup of contaminants such as heavy metals or pesticides in living organisms. Aquatic organisms are often subjectto bioaccumulation because they absorb contaminants from the water around them faster than their bodies are able to excrete them. Humans are alsosubject to bioaccumulation, either from consuming contaminated aquatic organisms or from exposure to contaminants in our food, air, or water. Heavy metals do not biodegrade, which means they can last for a long time in our bodies.

Bioaccumulation_graphic_f52cb486-f663-4ae4-a619-93dca87872dd.png

Bioaccumulation in the food chain begins with the smallest microorganisms and ends with humans. Heavy metals are able to bind to the surface of microorganisms (like phytoplankton in oceans) and sometimes enter the cells themselves.

Once they enter the cell, heavy metals can react with chemicals released by the microorganism to digest food, and undergo chemical transformations. (An example is mercury becoming methylmercury, which is especially dangerous because methylmercury is more easily absorbed by living organisms.) Insects and zooplankton eat microorganisms, fish eat zooplankton, and eventually humans order a tuna to eat at a restaurant!

At every point in this process, heavy metals bioaccumulate in the bodies of each living organism — by the time they get to us, we consume the heavy metals in high concentrations. The increase of heavy metals concentration up the food chain is called biomagnification.

Health Effects of Heavy Metals

Unfortunately, heavy metals can have serious health effects for humans. Many play a role in cancer development or cause internal organ damage, even at low concentrations. Cadmium, cobalt, lead, nickel, and mercury are also known to affect the formation of blood cells–the metals can react with the surface of the cells, making them less elastic and therefore less able to circulate throughout the body. Here we’ve summarized five critical heavy metals and their known health effects:

Mercury

Mercury is known to cause brain damage in developing children, and if you’re pregnant, it can cause birth defects or possibly a miscarriage. Methylmercury compounds are also known to cause cancer. There is a deep concern about mercury exposure through predatory fish such as tuna, which is the second most popular fish in the US. An example to demonstrate the magnitude of the issue is if a 45 lb child eats one 6 oz can of white tuna per week, the child is already exceeding the US Environmental Protection Agency (EPA) mercury limit.

Lead

Lead is particularly harmful for children. It is structurally similar to calcium and can therefore replace calcium in the growing bones of children. Once the child is grown, the lead can release into the body and cause brain and nerve damage. Lead can also cause anaemia, reproductive issues, and renal impairment. People are usually exposed to lead through contaminated food or water, or in the case of children, from ingesting objects with lead paint. Lead can be expelled at very low levels, but at high or continuous doses, lead bioaccumulates in the body.

Cadmium

Cadmium remains in human bodies for decades, and long-term exposure is linked to renal dysfunction. A high concentration exposure can also lead to bone defects and lung disease, which may eventually become lung cancer. People can be exposed to cadmium not only through food and water, but also from tobacco in cigarettes.

Chromium

At low levels, chromium only causes skin irritation and ulcers. Longer-term exposure, however, can lead to liver issues, renal tubular damage, and cancer. Similar to mercury, chromium easily accumulates in aquatic life.

Arsenic

Arsenic is technically considered a metalloid, but acts like a heavy metal in its toxicology. Arsenic exposure can cause breathing problems, lung and skin cancer, decreased IQ, nervous system issues, and even death at high levels. Arsenic easily enters groundwater and soils from natural sources and industrial operations. Some crops can uptake arsenic after irrigation or from the soil, an example being rice, leading to exposure through food.

How to Reduce Your Exposure

Though these health effects may seem frightening, there are a few simple ways to reduce your exposure to heavy metals and protect your health! A few include:

  • Avoid certain fish: Specifically, fish that are high in mercury such as king mackerel, swordfish, marlin, & tilefish. It is particularly important to reduce tuna consumption, especially in the form of tuna steaks or canned white albacore. For other options, check out this guide to eating sustainable and lower-risk fish.
  • Read medicine labels: Some may contain heavy metals as ingredients.
  • Minimize rice consumption: There is evidence that rice contains arsenic and thus increases cancer risk. Rinsing rice before cooking may reduce risk.
  • Stop smoking tobacco: Arsenic, lead, and cadmium levels have been detected in cigarettes and e-cigarette vaporizers.
  • Be aware of lead pipes & filter your water: This concept is addressed further in Part 2 of this article–where we’ll focus on heavy metal exposure and remediation. Essentially, because heavy metals can enter groundwater or leach from pipes, it is important to filter them out before drinking water.

Have more questions? This source offers extensive details about the environmental occurrence of specific heavy metals, how humans are exposed to them, and their toxicity/carcinogenicity.

Or, feel free to email us at contact@simplewater.us!

Sources: 

https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/bioaccumulation-heavy-metals

https://ehp.niehs.nih.gov/1205875/

https://saferchemicals.org/get-the-facts/chemicals-of-concern/heavy-metals-2/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4144270/

https://www.fda.gov/downloads/Food/FoodScienceResearch/RiskSafetyAssessment/UCM486543.pdf

https://www.sciencedirect.com/science/article/pii/S2214750014001292

https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/bioaccumulation

https://www.webmd.com/baby/4-common-causes-miscarriage#1

https://www.whoi.edu/oceanus/feature/how-does-toxic-mercury-get-into-fish

https://www.ncbi.nlm.nih.gov/pubmed/19868909

https://data.web.health.state.mn.us/lead

https://www.atsdr.cdc.gov/csem/csem.asp?csem=34&po=6

https://www.merriam-webster.com/medical/bioaccumulation

https://www.jhsph.edu/news/news-releases/2018/study-lead-and-other-toxic-metals-found-in-e-cigarette-vapors.html

https://www.publicdomainpictures.net/en/view-image.php?image=51520&picture=fish-in-lake-2

https://commons.wikimedia.org/wiki/File:Tara_River_Underwater.jpg

Is My Water Radioactive?

No, we’re not asking if your water is turning you into a monster...radioactivity in water is a real threat.

RadioactiveWater-Title_1024x1024.png

Radioactivity is not scary in the way that movies and popular culture depict. Sadly, it is much stealthier–it can cause irreparable damage to your body that stays hidden for years, or even across generations.

We are exposed to natural radiation in our daily lives (an example being bananas!). Radioactive particles, or radionuclides, are a part of the natural world–they exist in plants and animals usually as potassium-40 or radium-226. However, increased exposures to radiation occurs in our water or air when nuclear power plants, mining operations, or laboratories release radioactive materials into the environment.

Tap Score has written this guide to help you understand what radiation really is, what the associated risks are, and what types of radioactive elements are common in drinking water, and how they should be treated.

Getting the Terms Right: What Are Radioactive Particles?

Radiation refers to any process that emits energy in the form of electromagnetic waves or particles, such as light or sound. When we talk about radioactive particles, we are specifically referring to ionizing radiation. Ionizing radiation is radiation that causes an atom or molecule to lose electrons and become charged–this charged molecule is called an ion.

Radioactivity is “the act of emitting radiation spontaneously”. An atom can be radioactive when it is unstable and wants to dissipate some of its energy to reach a more stable form.

The different “forms” of stable or unstable radioactive elements are called isotopes. We distinguish these radioactive isotopes by their mass, which is attached to the end of the element name, like Uranium-238.

Radioactive Particles in Water are Alpha or Beta

Radioactive particles are present in rocks and soil, which usually serve as the path to enter groundwater. The two types of radioactive particles present in water are alpha and beta particles–which are present in different sizes and element types.

Alpha particles consist of two protons and two neutrons. Common examples in water are radium-226, radon-222, uranium-238, polonium-210, lead-206. While alpha particles cannot penetrate skin from the outside, they are active in the body and can cause damage if consumed.

Beta particles are radioactive particles made up of one electron. Common examples in water are strontium-90, potassium-40. Beta particles can penetrate the top layer of skin and cause burns. Beta particles likely cause more damage inside the body than alpha particles–they have more energy and can therefore travel farther into body tissue than alpha particles can.

Radioactive Particles in Water

We are concerned about naturally occurring radiation and additional radioactive particles that enter water from rock formations near mining sites, nuclear power plants, or laboratories. Radon, in particular, occurs in gaseous form in soils and can dissolve into groundwater or enter homes as a gas through the basement. Exposures to radon in both air and water are seriously concerning–here, we focus on exposure through drinking water.

Prevalence of Radioactive Particles: Private Wells at Higher Risk

The Environmental Protection Agency (EPA) sets standards for radionuclides in city treated drinking water, but if you are a well water user you are at a much higher risk for radioactive contamination. In a study conducted by the United States Geological Survey (USGS) on radioactive particles in well water, the most abundant element above the EPA health threshold was radon, appearing in 65% of wells. Uranium was present in only 4% of the wells– which makes sense because radon is produced as uranium decays.

Signs that You Have Radioactive Particles in Your Water

Unfortunately, there are no obvious signs of radioactive particles. The only way to identify radon and uranium in your water is through testing. As a company that tests water, we’ve made this pretty easy–our essential test and advanced well water tests include uranium testing, we offer a specific test for radon, and we’ve developed a full radiation test that measures Gross Alpha and Gross Beta particles.

How do radioactive elements in water affect my health?

Unfortunately, the effects from radioactive particles in water can cause cancer and even be fatal. While our skin can protect us against alpha particles in the environment, exposure to radiation through water is particularly dangerous because radioactive elements damage tissues and organs.

Radioactive particles cause damage by breaking chemical bonds essential to our body’s functioning. Changing bonds in a molecule drastically alters its ability to function. Radioactive particles can cause cells in our body to die or slow down their reproduction. If a group of cells crucial to bodily function dies, the effects can be fatal.

After the bonds of normal cells in the body are broken, they release electrons. This can create a chain reaction that can eventually impact DNA molecules. Mutations are consequent to DNA damage, which lead to cancer. And, if germ (sex) cells are mutated, the cancer can be transmitted to children long after the initial exposure. The results of a study done in Iowa show that towns with radium-226 present in their water supply had higher rates of lung, bladder, and breast cancer.

How to protect yourself from Radioactive Particles in Water

Treatment

There are two primary treatment options for radioactive particles in water–carbon filters and ion exchange:

  • Carbon filters are one option for removing radium and strontium from drinking water. However, if radon is also present the filter must be changed very frequently–carbon can adsorb radon and lead to higher radiation exposure if radon is left to build up. As radon particles accumulate, they may fall out of the filter and back into the water stream.
  • Ion exchange can be used to treat uranium. However, ion exchange creates backwash that contains high concentrations of radionuclides, which makes disposal a concern.

Ultimately, the type of treatment you choose depends on what type of radiation problem you have.

Test Before You Treat

Though these health effects may be frightening, they can be prevented or at least mitigated.  Tap Score offers a Full Radiation Water Test to measures alpha and beta particles as well as a specific Radon Test to help you determine if you are at risk. We’ll also help you choose the right treatment options if you discover a problem. Picking the right filter matters to ensure you properly treat your water.

Have more questions? Feel free to email us at hello@simplewater.us! 

Sources: 

https://ehss.energy.gov/ohre/roadmap/achre/intro_9.html

https://academic.oup.com/aje/article/116/6/924/189051

https://www.wqpmag.com/radiation-water

https://www.epa.gov/dwreginfo/radionuclides-rule

https://www.circleofblue.org/2011/world/water-testing-reveals-trace-elements-exceed-health-standards-in-20-percent-of-wells/

Your Water’s General Chemistry

Everything You Want to Know About Hardness, Alkalinity, Total Dissolved Solids, and pH

Water Chemistry.png

There are many technical terms surrounding the general properties of your drinking water, but this shouldn’t stop you from knowing your water’s fundamental chemistry. Rather than leaving you to scratch your head (and search Google for hours), we’ve assembled this easy guide to help you understand what each of these important water properties mean – hardness, alkalinity, total dissolved solids (TDS), and pH. We think everyone who drinks water (i.e., everyone!) should know about these main water properties and why they matter.

Hardness

What is Hard Water?

cWater is normally considered “hard” if it contains high levels of dissolved and positively charged minerals like calcium and magnesium. 85% of U.S. drinking water has some degree of hardness and while it is not a health hazard, it can be a bother to your pipes, faucets, and other water fixtures

Water that lacks these hard minerals is called soft water. You’ll most likely hear about hard water and a water softener in the same context. This is because a water softener is a treatment device or water conditioning system that removes hard minerals from water and usually replaces those minerals with something less problematic. Water that has been treated or conditioned by a water softener will taste differently than hard water, and leave less of a residue on fixtures.

Why Care About Water Hardness?

Hard water is likely to leave mineral deposits on everything it touches. This means that hard water can cause many problems in a home or for a business.

  1. Hard water can clog pipes through formation of mineral deposits called, scale.
  2. Hard water can leave marks on sinks and baths and toilets
  3. Hard water may prevent your soap from forming bubbles
  4. Hard water can cause expensive malfunctions and damage to water related equipment like heaters, kettles and cooling towers.

Hardness is not inherently bad however. A small amount of water hardness is actual good for your tap water because hard elements like magnesium and calcium will naturally coat the inside surfaces of your pipes and protect them from corrosion.

Water Hardness and Health

Often when we discuss water quality and health, we only think about the negative impacts. This time we’ve got some good news: Hard water can be beneficial. The National Research Council states that hard water generally contributes (between 5-20%) toward total calcium and magnesium dietary needs. While there is some evidence linking water hardness to other health conditions, it’s not yet been made fully clear what (if any) positive or negative health impacts there may be. Water hardness above 400 PPM however, may very well be considered hard enough to merit treatment for the sake of avoiding potential health impact. Even though there is no fully agreed upon health concern yet endorsed by the scientific community, at a high enough level of hardness there may be good reason to consider eliminating treating the underlying causes.

Some water softeners work based on “ion exchange”, where calcium and magnesium (“water hardness ions”) are exchanged for sodium ions in your water. It’s unlikely that the extra sodium in your water will cause a health problem, but if you have high blood pressure, you can avoid worrying about the added salt content by choosing “salt-free water softeners” (they tend to use potassium chloride ions).

Water Hardness by the Numbers

There are different subjective interpretations of hard and soft water. Here is a good general guide for classifying your water’s hardness measurement.

Hardness table.png

* In order to find an equivalent unit to measure all ions that make up water hardness, engineers measure hardness as ppm of Calcium Carbonate because is easy to measure and one of the primary sources of water hardness.

You might see that water hardness is measured with varying units:

  1. Milligrams per liter (mg/L) of calcium carbonate (CaCO3)
  2. Parts per millions (of calcium carbonate)
  3. Grains per gallon (gpg)

We know that all these units can get confusing, here are some useful ways to convert from one unit type to another:

1 Grain = 17.1 mg/L of CaCO3
1 mg/L of CaCO3 = 1 PPM of CaCO3

What You Can Do About Water Hardness

If you want to avoid hard water for any reason, there are two main water softening options you can consider:

  1. Invest in a water softener that uses salt-based ion exchange technology
  2. Invest in a water softener that uses non-salt-based technology
  3. Invest in a Reverse Osmosis treatment system (but you’ll need to maintain your RO often if your water hardness is high and this can be expensive.)

As described above, you may even need to add some hardness to your water if your water is too soft. Doing so means adding minerals like calcium or magnesium back into your water with a special remineralization filter. Having some hardness in your water is good for your pipes because it can protect them from the corrosive effects of overly soft water.

It’s worth noting that since water hardness usually effects the entirety of a water system (pipes, faucets, showers, pumps, other equipment) that water softeners are generally only installed at the facility or whole-home level. You won’t often install a softener and just one tap, rather you’ll find that most products are designed for the full home or building. Such systems are called Point of Entry (as opposed to Point of Use).

Total Dissolved Solids

What Is Total Dissolved Solids (TDS)?

Due to its property as a universal solvent, water can dissolve a wide range of other substances. While these “dissolved solids" may refer to any substance that you can’t see in your water. The term total dissolved solids (TDS) typically refers to these dissolved inorganic salts:

  • Calcium
  • Magnesium
  • Potassium
  • Sodium
  • Bicarbonates
  • Chlorides
  • Sulfates

Plus, small quantities of dissolved organic matter.

Ultimately, total dissolved solids (TDS)  is considered to be the sum of all inorganic and organic substances in the water.

In the United States, elevated TDS in water is often attributed to natural environmental features–such as mineral springs, salt deposit, and seawater intrusions. However, other sources of TDS in drinking water may come from:

  • Sewage
  • Urban or agricultural runoff
  • Industrial wastewater
  • Chemicals used water treatment processes  
  • Road de-icing via salt

Why Care About TDS?

High TDS concentrations in your water are likely to cause aesthetic issues rather than health issues. Due to these possible effects, TDS is only listed as a Secondary Drinking Water Standard by the EPA–which means that they are governed by a non-enforceable guideline (rather than a mandatory standard).

Elevated TDS levels may result in:

  • An unpleasant taste (especially bitter or salty)
  • An unpleasant appearance
  • A film or precipitate on fixtures

Low TDS levels may result in:

  • Corrosion of fixtures or pipes
  • Reduced water filter efficiency

TDS and Health

While TDS does not have a direct effect on your health, and may only result in technical and aesthetic issues, extremely high TDS levels can indicate that potentially harmful contaminants (such a manganese, arsenic, or iron) are present in your water.

TDS By the Numbers

TDS table.png

What You Can Do About TDS In Your Tap Water?

The best way to lower TDS in your tap water is to invest in a reverse osmosis water filter. Most RO systems will remove at least 95% of the TDS in your water.

pH

What is pH?

pH is a measure of something’s acidity or basicity (sometimes referred to as alkalinity.) More specifically, pH measures the relative amount of free hydrogen and hydroxyl ions in the water. The pH scale ranges from 0 (acidic) to 14 (basic or alkaline). A pH of 7.0 is neutral. Water with more free hydrogen ion is acidic, while water with more free hydroxyl ions is basic.

Most tap water should fall in the range of 6 - 8.5. It’s important to note that the pH scale is logarithmic–meaning that each step on the scale corresponds to a ten-fold change in acidityFor example, water with a pH of four is ten times more acidic than water with a pH of five.

Why Care About pH?

Shifts in tap water pH can be caused by many different types of chemicals–making pH a crucial indicator of chemical changes and health of your drinking water.

Water with high pH may cause:

  • Bitter taste
  • Mineral deposits on pipes, faucets, and appliances
  • Reduced effectiveness of chlorine disinfection
  • Altered speciation of organic and inorganic compounds in your water
  • Increased corrosivity

Water with low pH may result in:

  • Increased corrosivity
  • Altered speciation of organic and inorganic compounds in your water
  • General increase in the solubility of metals

pH and Health

pH will most often not directly affect your health. However, the U.S. EPA, classifies pH as a secondary drinking water standard and recommends a pH between 6.5 and 8.5 for drinking water. If your water pH is outside of these limits then there is a stronger likelihood for pipes and fixtures to corrode metals into your drinking water and there is also the chance that a nearby landfill may be leaking into your water supply.

Low pH levels (below 5) can have seriously harmful health effects on local wildlife like fish and pets.

pH by the Numbers

What You Can Do About pH in Your Drinking Water

If you’re tap water pH is too low (below 6) you may consider any one of several known treatment solutions in order to raise the pH of your drinking water.

  1. Installing a water softener to add alkali-rich compounds into your water
  2. Installing a neutralizing filter to raise your water to near pH 7
  3. Installing a sodium hydroxide injection feed pump
  4. Adding lemons or baking soda in your glass (temporary fix)

If your tap water pH is too high (above 8.5) and you taste a chalky bitterness in your water, then you may consider lowering your pH by installing an acid injection system. 

Alkalinity:

What is Alkalinity?

Alkalinity is a buffer for your water’s pH. This means it is a measure of your water’s ability to resist changes in pH level. Alkalinity “does this” by neutralizing weak acids that may enter your water on the way to your tap.

Alkalinity in tap water is normally expressed as the sum of concentrations of bicarbonate, carbonate, hydroxide, and some phosphates and silicates. Alkalinity in your water usually originates from limestone-like deposits that dissolved into your water source (a well, an aquifer, etc.)

Why Care About Alkalinity?

Alkalinity mitigates changes to your water’s pH. This makes alkalinity important because swings in pH often lead to many other noticeable and un-noticeable changes in your overall water quality. Such changes may very well relate to your water’s health and maintenance concerns. In general, you don’t want your water pH swinging up and down or else your water quality and water health will be hard to predict.

While lower alkalinity waters can be more corrosive (i.e. low alkalinity allows weak acids enter the water supply they are more likely to lower the pH), higher alkalinity waters above 150 mg/L are more likely to form scale (i.e. mineral deposits) on your pipes and other fixtures–making your plumbing system less effective.

Alkalinity is not detrimental to humans, and can often have a positive impact on your pipes and water distribution system. When combined with hardness, moderately alkaline water (less than 300 mg/L) can form a layer of calcium or magnesium carbonate that can inhibit or reduce corrosion of metal pipes. Note: most water distributors try to make your water slightly alkaline; striking a balance between coating the pipes with a safe level of calcium carbonate, but not so much so that pipes are damaged or your heater’s efficiency is affected.

Alkalinity and Health

There is currently no health standard for alkalinity in drinking water.

While many bottled water companies have released alkaline water products in the past several years, their claims that alkaline water provides health benefits are largely unproven by the general science and health community. Alkaline water companies may claimed that alkaline water slows aging; increases energy levels; helps with fertility; and helps you regulates your body’s pH level to prevent chronic diseases like cancer. None of these claims have been proven.

Alkalinity by the Numbers

Alkalinity table.png

In general, you want your water’s alkalinity measurement to fall within 75% - 100% of your water’s hardness measurement (assuming both measured as CaCO3, calcium carbonate.) This is because, when reported in mg/L of calcium carbonate, alkalinity and hardness are nearly equal in concentration–as they generally come from the same minerals 

Note: Do not confuse “alkaline water”  (high pH water with more OH- ions than H+ ions), with water “alkalinity” (water’s ability to neutralize acid and keep pH stable.)

What You Can Do About Alkalinity

Since a broad range of alkalinity in drinking water is considered acceptable, it is not often that folks need to alter their natural water alkalinity. A low level of alkalinity is desirable in tap water because it serves as a buffer that prevents large swings in pH. If there is not enough alkalinity in your water (perhaps because a Reverse Osmosis treatment machine took it all out) then you may try the following approaches to raise your alkalinity (and pH):

  1. Add a remineralization filter to add minerals back into your water
  2. Install a water distiller which will remove acids in the water
  3. Install a water ionizer to separate acidic and basic water

For more information

For more information about other water quality characteristics, take a look at our blog, Tips For Taps, or email us at hello@simplewater.us!

Sources: 

https://water.usgs.gov/edu/hardness.html

https://adams.uwex.edu/files/2013/01/Home-Water-Safety-Interpreting-Drinking-Water-Test-Results.pdf

http://www.dph.illinois.gov/sites/default/files/publications/drinking-water-042716.pdf

https://www.water-research.net/index.php/water-treatment/tools/total-dissolved-solids

https://extension.psu.edu/corrosive-water-problems

https://water.usgs.gov/edu/qa-solvent.html

https://www.epa.gov/dwstandardsregulations/secondary-drinking-water-standards-guidance-nuisance-chemicals

https://www.wqa.org/Portals/0/Technical/Technical%20Fact%20Sheets/1993_ConsumptionOfLowTDSWater.pdf

https://www.safewater.org/fact-sheets-1/2017/1/23/tds-and-ph

http://www.who.int/water_sanitation_health/dwq/chemicals/ph_revised_2007_clean_version.pdf



| HOME | GET TAP SCORE | CONTACT US | FOR THE PRESS |