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  • Writer's pictureDr. Venessa Madrigal

Effects of Chlorinated Water on Health, Water Filters

Updated: Oct 4, 2021

The U.S. Environmental Protection Agency (EPA) sets legal limits on over 90 contaminants (i.e. microorganisms, organic and inorganic compounds) in drinking water. Prior to water quality regulations, many people became ill and/or died because of contaminated water. The Portland Water Bureau tests for more than 200 regulated and unregulated contaminants in the drinking water, which comes from aboveground sources like the Bull Run Water shed and the Columbia South Shore Well Field. Clark Public Utilities, which serves Clark County, WA, checks for more than 100 contaminants and their water supply is mainly from 4 underground aquifers - Recent Alluvial Aquifer, Troutdale Aquifer, Sand and Gravel Aquifer, and fractured basalt formations.

Local water management companies/organizations must adhere to state and federal water quality regulations. The U.S. Environmental Protection Agency (EPA) is responsible for establishing federal standards through the Safe Drinking Water Act (SDWA). Per the SDWA website, "the [SDWA] gives individual states the opportunity to set and enforce their own drinking water standards if the standards are at a minimum as stringent as EPA's national standards." Here are the Portland, OR, and Vancouver/Clark County, WA, sites for water quality information:

Portland Water Bureau, PWB:

Within Clark County, individual cities have their own sites:

Chlorine and/or ammonia are commonly added as disinfectants. In Portland, chlorine is added at the water source and then ammonia, which binds to chlorine to form chloramine, is added at the treatment center. Per the Portland Water Bureau: " Chloramines are a disinfectant that stays in water longer than chlorine. Using chloramines ensures that disinfection remains adequate throughout the entire distribution system while reducing the formation of disinfection by-products" ( In Clark County, WA, "only a trace of chlorine [is added as] necessary to ensure the water delivered to your home is free of harmful bacteria" (

In summary, Portland's water has chloramine and Clark County's water has chlorine.

Effects of chlorine

Disinfection of water allows for the water sources to become safe to drink. However, these chemicals can affect our health, especially at high levels, though some people are sensitive to them at low levels in the short term. At low levels of chlorine (0.06-0.3 parts per million, ppm), people can have a cough, burning/stinging of nose and throat; at 0.35 to 0.72 ppm: burning of the eyes (conjunctiva) and pain after 15 minutes; above 1.0 ppm: discomfort ranging from eye/ocular and respiratory irritation to coughing, shortness of breath, and headaches; at 30 ppm: chest pain, vomiting, difficulty breathing (dypsnea), and cough; and at 46-60 ppm: toxic pneumonitis and pulmonary edema

Ok, so what does that all mean? Well, amount and exposure time matters as to which symptoms and how severe the symptoms may be. Also, the body size of the person - baby vs adult, will results in differing effects as well. On Clark County's resource for contaminants, chlorine is not directly listed on the tested items; however, two of its byproducts were listed and were not detected to 2.5 parts per billion (much smaller than ppm). In The City of Vancouver's 2019 Water Report, chlorine was detected between 0.79-1.10 ppm, with the highest allowed listed as 4.0. The PWB 2020 Drinking Water Report showed total residual chlorine at 1.76-1.80 ppm.

What about effects of inhaled or ingested chlorine in the long term?

According the EPA's website, these are the chronic effects to the following:

Endocrine (hormonal):

Inhalation: "No information is available on the developmental or reproductive effects of chlorine in humans or animals via inhalation exposure"

Ingestion: "Animal studies have demonstrated no evidence of reproductive or developmental effects from ingestion exposure to chlorine." Note that this does not state that testing was done in humans.


Inhalation:"No information is available on the carcinogenic effects of chlorine in humans from inhalation exposure."

Ingestion:"Several human studies have investigated the relationship between exposure to chlorinated drinking water and cancer. These studies were not designed to assess whether chlorine itself causes cancer, but whether trihalomethanes or other organic compounds occurring in drinking water as a result of chlorination are associated with an increased risk of cancer. These studies show an association between bladder and rectal cancer and chlorination byproducts in drinking water." However, note that the EPA has not classified chlorine as a carcinogen (cancer-causing substance).

How can chlorine can affect the endocrine/hormonal system?

In general, the endocrine system is made up of organs & glands that release hormones to allow our body to function. states that the endocrine system is comprised of "glands and organs that make hormones and release them directly into the blood so they can travel to tissues and organs all over the body. The hormones released by the endocrine system control many important functions in the body, including growth and development, metabolism, and reproduction. The endocrine system includes the hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid glands, thymus, adrenal glands, and pancreas. It also includes the testes in males and the ovaries and placenta (during pregnancy) in females."

There are organic and inorganic compounds that can negatively affect the endocrine system and these are called endocrine disruptors compounds (EDCs). Many of these diverse compounds "contain halogen group substitutions by chlorine and bromine. They often have a phenolic moiety that is thought to mimic natural steroid hormones and enable EDCs to interact with steroid hormone receptors as analogs or antagonists", which means that they can mimic a hormone and do what that hormone usually does (as an analog) or do the opposite of that hormones function (antagonist). These compounds can affect ones health starting generations back, not just the substances to which a person is exposed to in their own life. A person's biological mother influences their health outcomes based on her exposures and her health was influenced by her mother's exposures, and so on.

EDCs affect many aspects of one's health and their offsprings' health. More info can be found in this very lengthy article:

Are the by-products of chlorine affecting our health?

Noutsopoulos et al propose that the by-products of chlorine might be more harmful than the contaminants that chlorine is disinfecting.

Noutsopoulos C, Mamais D, Samaras V, Bouras T, Marneri M, Antoniou K. Effect of wastewater chlorination on endocrine disruptor removal. Water Sci Technol. 2013;67(7):1551-6. doi: 10.2166/wst.2013.025. PMID: 23552244.

Water filters

Water filters can prevent chlorine and chloramines from passing through our drinking and bathing water. The Portland Water Bureau recommends "NSF/ANSI Standard 42 certified filters for reducing chloramines for consumption. The NSF/ANSI Standard 177 is for showerheads that reduce free chlorine. Since Portland uses chloramine (chlorine + ammonia) and not free chlorine, filters with the NSF/ANSI 177 standard may not work effectively. Some certified granular activated carbon showerheads claim to reduce chloramine." Since Clark County uses chlorine and not chloramine, the filters with the NSF/ANSI 177 standard may work effectively.

Here are some recommendations for NSF 42 filters:

Multipure has various filtration systems; however the shower head filter is not NSF 42 certified:

For bathtubs:

Multipure Aquasplash - filters up to 100% (Chlorine), 25% - 30% (Chloramine)

Shower Filters:

Aquasauana: Filters 10,000 gallons, average replacement every 6 months, 1 yr warranty. Base filter without shower head $80 (as of Dec 2020); filter replacement $52.50 (as of Dec 2020).

Here are some recommendations for NSF 177 filters:

Multipure Aquashower Filter:

Filters 25,000 gallons

Shower head w/ filter: $56; replacement filter: $27 (as of Dec 2020)

Pelican Water Systems:

Pelican Shower Filter: Filter lasts 15,000 gallons or 750 ten-minute showers; average replacement every 6 months. Price: $170 (as of Dec 2020).

I have no financial affiliations.


Best wishes for your and your loved ones' health!

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