NDMA – Cancer in China’s tap water?

NDMA Cancer in China's tap water?

Summary: We have received many inquiries lately about the water contaminant NDMA and whether it poses a health risk in filtered water. The answer is no, based on levels found in the recent studies, there is no significant cancer risk from NDMA in drinking even unfiltered tap water.


Why is NDMA in the news recently?

Recent news articles focused on a Tsinghua University School of Environment study which listed levels of the chemical NDMA found in Chinese water. The majority of both Chinese and English media articles misconstrued the original study findings, with the worst articles giving the false impression that this is a significant finding of a major cancer risk. Additional misinformation was presented regarding international guideline levels and the ability of various filtration technologies to remove NDMA.

Most of the inquiries we received were from the ChinaWire wechat posting which was copied from a China Daily article “Cancer agent found in 44 cities’ drinking water

To clear up the confusion surrounding the matter, we will address recent questions. To simplify things, this article will list all values in nanograms per liter (ng/L)

1 ug (microgram) = 1000 ng (nanogram)

What is NDMA?

NDMA (N-Nitrosodimethylamine) is a chemical, usually formed in water supplies from the interaction of chloramine (used as a water disinfectant in many Chinese cities) with nitrogen compounds in water, or with equipment (such as rubber seals) in the water distribution system. See the Resources & References section at the end of this article for more information.

Is NDMA dangerous?

Yes, NDMA is associated with cancer risk in humans, based on animal studies. There are also cases of individual developing cancer after being given massive doses of NDMA. However, risk is based on concentration. At the levels found in Chinese tap water, there is no significant cancer risk from NDMA.

What NDMA levels were reported in the recent Chinese study?

The following is paraphrased from the original study, with a focus on tap water: Nitrosamine levels were measured in 164 water samples of finished water, tap water, and source water from 23 provinces, 44 cities from large cities to small towns, and 155 sampling points all over China over the previous three years. NDMA was found in 41% of the tap water samples. The average NDMA concentration in tap waters was 13 ng/L, across all tap water samples, with a mean concentration of 32.3 ng/L among the detected samples.

What are the actual guideline levels for NDMA?

WHO guidelines are 100 ng/L. Japan and Australia also adopted 100 ng/L, Canada is the lowest at 40 ng/L. China and the US governments have not yet adopted national guidelines (but certain US states have). The media articles incorrectly implied that California has a maximum permitted level of 10 ng/L. Actually that is California’s Notification Level which simply means that at 10 ng/L, it is recommended (not required) that the water utility inform the consumers, either in an annual report or other method, that NDMA levels have exceeded 10 ng/L. The Response Level is when it is recommended (not required) that the utility change their supply water, or make other steps to notify the public. The Response Level for NDMA in California is 300 ng/L.

What is the actual risk of NDMA at the Chinese study levels?

The Canadian guidelines of 40 ng/L are the closest to the Chinese study averages of 32.3 ng/L, so I will use them to approximate the study risks. Where did the Canadian guidelines come from? First, an analysis was done of the rat cancer studies to find a conversion to calculate risks to human. Conservative adjustments (allometric scaling) were made, acknowledging the high toxicity of NDMA and the possibility that it may be more damaging to humans than to rats. Human exposures were based on an average human adult bodyweight of 70kg, drinking 1.9 liters of contaminated water per day, over the course of 70 years. The resulting calculations determine that NDMA drinking water contamination levels of less than 40 ng/L (drinking 1.9 L per day over 70 years) will only produce a 10^-5 (1 in 100,000) increased cancer risk, which is defined by the government as “essentially negligible”. WHO followed the same calculations but didn’t using allometric scaling, resulting in a higher guideline of 100 ng/L. California law also defines “no significant risk” as 10^-5 with their resulting calculations arriving at 30 ng/L. From the standards we can see that the Chinese study’s mean concentration of 32.3 ng/L holds no significant risk according to even the most stringent current international standards. The average of 13 ng/L across all tap water samples is close to a 1 in a million increased cancer risk which is considered de minimis or “essentially zero” by the US EPA.

OK, so the study NDMA averages show no real risk. Will my water filters remove NDMA anyway?

The WHO states:

“The most common process for NDMA removal is UV irradiation. A concentration below 0.005 µg/litre should be achievable by UV irradiation provided that the water is not grossly contaminated. NDMA is not removable by air stripping, activated carbon adsorption, reverse osmosis or biodegradation.

Reverse osmosis has partial removal in some studies, but will almost certainly not work in China due to the use of chloramines (which are a major cause of the NDMA in the first place), the resulting RO membrane degradation, localized hard water and high sediment levels which cause RO membrane fouling.

All the reference sources say that high powered UV will work for NDMA removal. Is there a version for my home?

UV at an intensity of 1000 mJ/cm2 will remove ~90% of NDMA. Most non-municipal UV systems have a target intensity of 30 to 40 mJ/cm2 for disinfection. However, oversizing a UV system to match water flow rates will allow you achieve 1000 mJ/cm2 intensity. For example, the Viqua E4 system (when used with a 1.89 liter per minute drinking filter) will provide approximately 1280 mJ/cm2 to 1440 mJ/cm2. Please contact us for more information.

Should I switch to bottled water from filtered water?

In my opinion, the main water concern in China should be about cancer-causing chemicals from agricultural, industrial and water disinfection sources. The activated carbon block technology we recommend for water filtration is recognized as the best possible technology for removing these chemicals. A properly certified carbon technology filter is recommended by the U.S. National Institutes of Health President’s Cancer Panel Report as one of the top ways to reduce environmental cancer risk:

Filtering home tap or well water can decrease exposure to numerous known or suspected carcinogens and endocrine-disrupting chemicals. Unless the home water source is known to be contaminated, it is preferable to use filtered tap water instead of commercially bottled water.

Bottled water, regardless of brand, has the potential to contain many chemicals and contaminants that will be removed by a proper filtration system. NDMA at found levels is not a cancer risk and changing to bottled water based on the news media reports would be a wrong decision.

Resources and References

Wikipedia has a simple summary https://en.wikipedia.org/wiki/N-Nitrosodimethylamine. The WHO is an objective source regarding conservative guideline values (100 ng/L) and general information http://www.who.int/water_sanitation_health/dwq/chemicals/ndmasummary_2ndadd.pdf. Canada, once again a world leader in progressive and aggressive guidelines (40 ng/L) to protect its citizens, has a particularly informative page on NDMA
http://healthycanadians.gc.ca/publications/healthy-living-vie-saine/water-nitrosodimethylamine-eau/index-eng.php Australia has an excellent fact sheet as well www.waterra.com.au/publications/document-search/?download=746 as does the US EPA https://www.epa.gov/sites/production/files/2014-03/documents/ffrrofactsheet_contaminant_ndma_january2014_final.pdf

Bad Air is Back! Be Sure to Check Your Filters.

Unfortunately, air quality has not been great this summer, and in the last few week Beijing has seen some particularly bad air days. With that in mind, it is especially important to make sure that your air filter machines are functioning properly and that the filter cartridges do not need to be replaced. Many machines we look at are not properly maintained, and the filters end up looking like the one above. If a machine is not regularly serviced the air that passes through it will no longer be filtered as thoroughly as it needs to be. In fact, if a machine is left unserviced for too long it can start making the air quality worse than if it weren’t running at all.

If you’re unsure how well your machine is working, or if it is time to replace the filter, feel free to contact us and one of our air quality experts will come test your machine and check out the filters at no cost to you, even if you did not purchase the machine from Raylient. Make sure your summer is filled with fresh air by ensuring your air filters are working as efficiently as possible.

Summer Days and Plenty of Haze

The Air Quality Index in Beijing has recently been hitting some dangerously high numbers. The heat and smog combined means the average person will be spending a lot of their time indoors. Unfortunately, without the right air filter, or a properly maintained air filter, the air inside your home can actually be worse than the air outside. Unsafe gases and particulate matter 2.5 microns or smaller (PM2.5) can increase beyond outdoor levels indoors due to leaks from outside, poor air flow, and the off gassing of many common building materials. The health effects of breathing in these pollutants can be severe and long lasting. Also consider that you and your family are breathing this in every single day, even while sleeping.

Having high quality air filters that are the correct capacity for your home is the first step toward ensuring you and your family are breathing safe and healthy air. Making sure your air filters are maintained and serviced regularly is also crucial. Unmaintained machines can actually make your air worse than not having a machine at all. Fortunately, Raylient offers a comprehensive guarantee and service package with all of its air filters, and it is the only company in China to do so. Take a look at our air filters, and then breath a sigh of relief knowing that no matter how hot or hazy it gets this summer, you can breathe safely.

Whole House Filter, Water Softener and Pressure Pump in Shanghai

Shanghai Whole House Filter, Water Softener, Pressure Booster Pump

This home in Regency Villas (御墅花园), Changning, Shanghai was recently completely renovated. To meet the owner’s requirements for clean, safe and soft water, Raylient installed an Aquasana EQ-600C whole house water filter and Aquasana EQ-AST-WH water softener.

For many years Regency Villas has a lower than normal water pressure. To resolve this problem and provide the home with a comfortable, stable water pressure, a Grundfos CM3-3 booster pump was installed.

Many times we are asked “should a water pressure boosting pump should be installed before or after a whole house filter?”. In almost all cases the pump should be installed after the filter system. If there is a sudden rise in the water pressure coming into the house, installing the pump before the system may cause a pressure spike that could damage a filter system (or softener, or UV system, etc). If the pump is placed after the system, a potential pressure spike will safety be distributed throughout the entire home’s plumbing system.

Free Vogmask!

In the past week we have seen the AQI hit above 300. If you have to go outside at all in conditions like that, you are going want to have a high quality air mask. Vogmasks are effective at filtering out hazardous nano-particles, and also have a carbon filter  to protect you from hazardous and odorous gases as well, something most other face masks tend to lack. Being the most stylish air mask on the market, they have the added benefit of not making you look like an alien.

Luckily enough, Raylient is offering a free Vogmask (normally sold for 225RMB) when you purchase a new air filter! Breathing safe air in your home or workplace is incredibly important, but it is also crucial to protect yourself when you are outside. Purchase a new air filter from Raylient from now until the end of July and you’ll be able to do both. Breath easy everywhere.