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The toxins in your tap water

Toxins in tap water

For all the years I lived in NYC, one of the most common refrains you hear is “the tap water in New York is the best.” I heard it repeated so many times that I believed it unquestioningly. It wasn’t until I saw research put out by the Environmental Working Group (EWG) that I started to have my doubts about drinking tap water anywhere, NYC or Omaha. Sure, America’s tap water is heavily regulated and won’t give you the stomach flu, it is “safe” to drink on some level, but the crisis in Flint should put everyone on notice: there is stuff in your tap water you can’t see or taste.

The EWG measures for levels of contaminants in water supplies that exceed what the EPA considers “safe” levels of toxins and carcinogens, and almost every major market has elevated levels of something, in some cases multiple levels of toxins are higher than recommended levels.

In my view, seeing this information makes some kind of water filter for your home obligatory.

Safe Drinking Water Act

The Safe Drinking Water Act requires the EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur and within an acceptable safety margin. While non-enforceable, these targets are called maximum contaminant level goals (MCLGs), and give a good idea of the water’s quality. The problem is they are routinely exceeded by cities across the country. 

So as not to pick on the Big Apple, we chose a city at random, which ended up being San Diego, and put their water supply to the test, looking for elevated levels of carcinogens and then rating based on our internal Science Grade to evaluate how much risk the tap holds for residents of “America’s finest city.”

The list below walks our readers through each contaminant and why it’s dangerous. San Diego water has 23 toxins over and above the safe limits set by the EPA, but we narrowed our focus to the most significant chemicals. The higher the Science Grade means more established science on the danger of that toxin.

Aaron takes over from here, giving the technical rundown for how some these chemicals react in the body.


Science Grade:

Probably highest up on the agenda due to the Flint water crisis is lead. The EPA has set the maximum contaminant level goal for lead in drinking water to zero as lead is a toxic metal that can be harmful to human health even at low exposure levels. Lead is persistent, and it can bioaccumulate in the body over time. Going beyond the EPA guidelines the federal Lead and Copper Rule, means that lead concentrations must be below 15 parts per billion (ppb) in 90 percent of households sampled. If this legal limit is exceeded, the water utility must apply measures to control lead leaching from water pipes.

Lead can get into drinking water through a variety of means, but is typically found in high levels when lead pipes, or pipes soldered with lead begin to corrode as in highly acidic or low mineral content areas. There are lots of regulations controlling the amount of lead that should be used in new houses and services, however there is a huge amount of existing pipework which contains very high levels of lead.

The health effects associated with lead are pretty staggering; in children for example it can lead to behavioral and learning problems, hyperactivity, slowed growth, anemia and hearing problems, and at very high doses seizures, comas and even death (R,R,R). Due to its bio-accumulation pregnant women are particularly susceptible with several issues surrounding fetal growth and development (R). This is outside of the other adult health effects such as increased blood pressure, decreased kidney function and reproductive problems (R).

There are also indirect health issues as evidenced by the Legionnaires’ disease spike which occured in Flint. Chlorine used in water treatment will normally effectively kill off Legionella bacteria. However, chlorine also reacts with lead to form an inactive compound. Due to the high levels of lead in the water, standard water treatment became ineffective leading to the spike in cases (R).


Science Grade:

Barium is a mineral commonly found in rocks and soil, and can commonly leach into the water supply. While soluble barium compounds are poisonous the insoluble forms found in the minerals and drinking water are relatively harmless at lower doses, with a health guidelines set at 700 ppb and the legal limit at 2,000 ppb. Health effects associated with barium include an increased cardiovascular risk and issues with muscle action and tone (R). As there is little industrial use for barium, the major source is likely to be from the surrounding land, and a map detailing areas of high concentration can be found here. However, the likelihood of breaching the described limits is very low.


Science Grade:

Bromoform is formed when chlorine or other disinfectants are used to treat drinking water. There is some evidence that it is associated with an increased cancer risk, however the science underpinning this is relatively inconclusive, as other factors may be associated with the increased risk (R). A health guideline of 5 ppb has been set, but again it is unclear what relevance this has to cancer risk.


Science Grade:

Chromium is a naturally occuring metal, which is often found in consumer and industrial applications. While in itself relatively harmless a particular form, hexavalent chromium, has been associated with an increased cancer risk. However, common chromium testing of water is not very accurate at determining hexavalent chromium concentration, and furthermore a safe level for this has not been determined. A legal limit of 100 ppb has been set for total chromium accordingly, although levels will be unlikely to reach this.

Estriol, estradioal, estrone and testosterone

Science Grade:

The first three of these are female sex hormones, with the latter being a male sex hormone. These hormones are sometimes detected at low levels in drinking water, and while there is no official health (their impact of biodiversity is well accepted [R]) guidelines some studies have suggested they may have a health impact when present in food (R,R). It is not clear if the levels detected in water can have as dramatic effect in humans.


Science Grade:

*This is based on health risk, the beneficial effects are well established.

Fluoride naturally occurs in most water sources, but is also added to many drinking water systems as a public health measure to improve oral hygiene. As such it is tightly regulated and a legal limit is set at 4 ppm. Because of its widespread use there is regular testing of water sources and it is unlikely that the 4 ppm level will be breached. Interestingly the level of effect in toothpastes was determined to be ~1,000 ppm ®. When present above these levels side effects can include nausea, vomiting and diarrhea, however this only occured in instances where the levels were approximately 50 times above the legal limit (R).

Haloacetic acids (HAA5)

Science Grade:

Haloacetic acids are a group of acids formed in water when chlorine is added as a disinfectant, and reacts with organic matter present in the water. Exposure to these acids has been associated with several poor health outcomes including increased cancer risk, and risk of birth defects (R,R,R), and as such a legal limit of 60 ppb has been set. Interesting a variety of treatment methodologies have been tested with filtration found to be the most effective (R).


Science Grade:

Molybdenum is a commonly found metal found in the soil, minerals and water, but is also commonly found in structural metals throughout the home. The current health guideline is set at 40 ppb, with a long term exposure beyond this level associated with gout like symptoms and increased uric acid levels (R,R).


Science Grade:

Strontium is a metal which can accumulate in the bones potentially affecting bone health, but also cardiovascular health (R,R). The radioactive form of strontium while less available has been associated with bone cancers and leukemias (R), an effect which was first described in those working on nuclear weapons or near to weapon test sites. A health guideline of 1,500 ppb for strontium as been set, the radioactive form is much less prevalent but should be avoided entirely.


Science Grade:

Vanadium is a metal commonly used in various steel, titanium and aluminium alloys and so the health effects of dust exposures are relatively well known. A health guideline of 21 ppb has been set for waterborne vanadium with effects in animal models showing increased blood pressure and mild neurological effects, and impacts such as stomach cramps and nausea in humans (R). However these doses were much higher than the health guideline quoted and so the health risk of waterborne vanadium is likely low.


Science Grade:

Xylenes are commonly used solvents in numerous industrial and consumer products, with paint thinner being a common example. Xylenes have been shown to have severe health impacts including damaging the central nervous system (R); however, because of this their usage and disposal is tightly controlled, especially in industrial settings. As such the health guideline of 1,800 ppb and legal limit of 10,000 ppb are unlikely to be breached.

Water filters

Although we did not include recommendations in the original version of this post, we have been asked in the comments section to include a list of water filters we like and use. As we discuss in our guide to water filters, the Berkey filter (pictured on John’s countertop in the photo for this blog) is one we like best as it is easy to use, highly effective, and also reasonably priced. The Berkey uses a simple two chamber system, combined with some of the best carbon filters on the market. Water is added to the top chamber and it is then forced through the two carbon filters, giving a clean supply of water in the bottom chamber which has a spigot.


Well, there you have it, there is more in your water than just water and minerals. We only touched on 11 of the 23 contaminants found in San Diego water and tried to offer a “non-alarmist” take. We are not here to claim that drinking San Diego water is going to make you sick. We also can’t say that drinking it for years is a good idea either. The point is the industry in this country is making its way into the water supply. We touched on it in our piece on nontoxic cookware, how C8, the chemical previously used to make Teflon can be found in most people’s blood. We also ran through the issues with flame retardants in mattresses, how those chemicals can bioaccumulate in human tissue. While Aaron clearly isn’t as alarmed with these findings as I am, no one can say for sure just how these chemicals affect people over time, especially when we all carry different capacity for detoxification thanks to polymorphisms in the SOD2, GSTP1 and other genes.

John O'Connor

John O'Connor is the founder of Gene Food, host of the Gene Food Podcast and a health coach trained at Duke's Integrative Medicine Program. Read his full bio here.

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