Testing for Trihalomethanes in Your Water (TTHM)

Chlorine has been used to disinfect water for almost a century due to its ability to kill bacteria and viruses in water. The use of chlorine as a disinfectant has been an effective contribution to public health eliminating plagues such as cholera and typhoid, and reducing the incidence of intestinal illness and other health problems caused by waterborne pathogens such as cryptosporidium. The benefits of disinfection, however, do not come without an effect.

Bromodichloromethane structureDepending on the disinfection procedure used (chlorination, chloramines, bromine, ozone etc.) and the chemical composition of the water prior to disinfection, many different organic chemical disinfection byproducts can form in drinking water. Trihalomethanes (THMs) are a byproduct of chlorine disinfection and to a lesser degree, disinfection using chloroamines. The THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) are formed when free chlorine combines with organic matter, like decaying vegetation commonly found in lakes and reservoirs. Total Trihalomethanes (TTHM) are regulated by the EPA at a maximum allowable annual average of 80 parts per billion. Some of the THMs are very volatile and will vaporize into air easily, so they may be inhaled while showering, however, the EPA has determined that this exposure is minimal compared to that from consumption. The Levels of THMs formed can vary widely on a number of factors including temperature, amount of chlorine used, season, and amount of plant material in the water, among others.

Chloroform structure
Some drinking water systems use chloroamines as a residual disinfection agent in place of chlorine. Chloroamine is not as reactive as chlorine and less THMs are formed. However, there are also drawbacks to chloroamine use. Chloroamine may cause nitrification and corrosion and may also increase exposure to other disinfection byproducts, such as N-nitrosodimethylamine (NDMA).

EPA Method 524.2 is used to analyze samples for TTHMs. This method involves concentrating the THMs from a water sample using a technique known as purge and trap. This technique isolates the volatile organic compounds (VOCs) from the water. The VOCs are then desorbed into a gas chromatograph/mass spectrometer (GC/MS) where they are separated, their identity is confirmed, and their concentrations are determined. Standard reporting limits for individual TTH with this method are 0.5 µ/L

58 Responses to “Testing for Trihalomethanes in Your Water (TTHM)”

  1. CHRISTINA P Says:

    I received a letter from my local water company stating that it was in violation of maximum contaminant levels for total trihalomethanes, however my 6 year old daughter has had 3 kidney infections in less than 2 months time. Can this be related to the problem?? And if so how can I avoid the situation?

  2. Dee O'Neill, Columbia Analytical Says:

    Hi Christina! Thank you for your question. We believe your inquiry is best suited for a health professional and recommend contacting your doctor or local health department. There is additional information on the EPA’s website which may also help (www.epa.gov).

  3. Eric R Says:

    Will a water softener or a reverse osmosis system with carbon filters help eliminate trihalomethanes in drinking water?

  4. Dee O'Neill, Columbia Analytical Says:

    Hi Eric! Thank you for your question. Probably the best source for information about water treament options would be the EPA and your State Department of Health. They can tell you which options would best fit your specific situation. Both agencies have websites for more information.

  5. Jean Says:

    I have the same question…the total in our trihalomethanes in town water is 83ppb. I have a reverse osmosis filtration system. Will this clean some of the trihalomethanes out? I didn’t find any resourses to answer this question.

  6. Columbia Analytical Says:

    Thank you for your question, Jean. There are many filtration systems on the market which have different capabilities. I would suggest you contact the manufacturer of your system and ask them specifically if their system filters out trihalomethanes (THMs) and under what conditions. If you want to be sure, we can certainly test the water coming out of your system to tell you whether there are still THMs present.


    THM_TOTAL <1.0



    I forgot to indicate that the units of the above are ug/l. I would appreciate your comments

  9. Beth, Columbia Analytical Says:

    The presence of Trichloromethane (chloroform) would probably indicate that the water is tap water. This might help to determine the source of your problem.


    Thank you for the reply. You are very kind.
    Can chloroform be found in nature or is it only found in water that has been treated with chlorine?

  11. Beth, Columbia Analytical Says:

    Chloroform may be generated by marine algae and in organic-rich spruce forest soil, aided by fugus.

  12. Elizabeth Smit Says:

    What is the fate of the THMs that are not consumed? Are they biodegradable?

  13. butch Says:

    today we received A notice that our water exceeded the stAndard TTHM level for over one year. My question, we found out three months ago that one of my labs have kidney problems and may be losing one kidney. could the TTHM level caused this. additonally, approximately one yeAr ago it was discovered that my other lab has crystals in his system and is is special food. could the TTHM level caused this also

  14. Dee O'Neill, Columbia Analytical Says:

    Hi Butch, try checking with your veterinarian about possible effects of TTHMs on dogs. The EPA website is also a good source of information about the toxic effects of the trihalomethanes.

  15. Sue Dye Says:

    Our water has been tested weekly, and for the past year, the County Regional Water System’s running annual average for THMs was 94.1 parts per billion (ppb).

    I am concerned, as this problem has gone on for a few years, and we are constantly receiving water notices, including boil water before drinking it. I am concerned about not only the safety of drinking the water, but breathing the water. The water company will not do anything for us. We are buying bottled water, but what else can we, as homeowners and residents, to protect ourselves, our children, the pregnant women and the sick and elderly of our community? And, how concerned should we be?

  16. Dee O'Neill, Columbia Analytical Says:

    Hi Sue!

    The article above states the EPA’s maximum contaminant guideline for trihalomethane (TTHMs) compounds is 80 parts per billion, so your water system is over the guidelines. The boil orders usually have to do with concern over bacteria in the drinking water due to any number of reasons (a break in the line, contamination at the source, chlorine treatment of the water failed for some reason, etc.)

    As stated in the article, chlorine is a substance that is used to disinfect drinking water and TTHMs form when the chlorine comes into contact with organic material in the water. Since bacteria can cause acute toxic effects, your water company must be very careful to make sure the drinking water is disinfected. When it’s not – you get a boil order. I would guess that your system is one that uses a lake, a reservoir and/or a river for one of its water sources (the organic matter source).

    I also imagine your water company would love to do something about this issue – unfortunately filtration systems or other systems that would help solve the problem are very expensive. They may not be able to afford a fix and may be aware that at this time further rate increases would be prohibitive. I would suggest that you contact your water company to find out what are the issues and if there’s a way you can help.

    Also – your water company informs you of boil orders and when the level of TTHMs (or any other contaminate that is monitored in drinking water) exceed the maximum contaminate level – so the community is being protected – they are being told when the water is not safe to drink.

    The EPA has stated that the amount of TTHMs that one can ingest by breathing is minimal and not a danger – but you are having to boil water, so it may be more of a factor for you depending on how often and how much water you boil. I would suggest you talk to your local health provider.

    Hope this helps! You can get more information about TTHMs from the EPA’s website.

  17. Dallas Says:

    FYI: On Monday (12/29/2008) we take it upon ourselves to test our water for
    TTHM levels using a local lab. Here are the results:

    Aqua water(Chuluota, Fl) to tap: 103 tthm (max of 80 is considered safe by DEP)
    Aqua through our home whole house system: 2.13
    Aqua/whole home filter/ through our sink tap reverse osmosis: ~0


    I wrote sometime ago and your reply was very helpful. I still have another query and i would appreciate if someone can shed some light to it.

    I have water running in my basement, constantly 24 hours a day for nearly 12 months. I suspect that it is drinking water from a burst pipe but the water company kep telling me that it is ground water. I analysed the water in teh basement and the tap water .the results of teh analysis are as follows:

    alkalinity…… mg/HCO3 165.7 152.9
    chloride…….. mg/C 30.1 29.1
    dibromochloromethane……..ug/l dichlorobromomethane……..ug/l trichloromethane……………..ug/l 0.21 12.4
    tribromomethane…………….ug/l calcium…………………………mg/l 65.3 84.8
    magnesium……………………mg/l 25.3 6.94
    hardness total………………..mg/l ca 107 96
    phosphorous………………….ug/lP 64 857
    Ph pHunits 7.2 7.4
    conductivity…………………..uS/cm 589 489

    The water flows through clay to reach my basement . is it possible that the components that constitute the trihalomethanes can dissolve and evaporate during this flow from the source to the basement ? if so by what approximate percentage and what factors can affect this ?

    Is there anyone on your team that knows mcuh about ground water or do you know anyone i can get in touch with about ground water?..looking at the two sample analysis what similarities are there between the two that can indicate that they are both from the same source?

    I would so much appreciate a reply from one of your team as this is causing me so much stress and i dont seem to be able to find anyone that knows much about water analysis

    Have a happy new year also.
    george georgiou


    I hope that the figures i showed you in my e mail of january 13th at 4.43 are clear. I tried to show them as a table but they somehow got bundled together. the first numerical total after each component refers to the basement water, whereas the second total refers to the tap water.
    thank you

  20. Dee O'Neill, Columbia Analytical Services Says:

    Hi George!

    I would suggest that you contact an environmental consultant in your area. They are qualified to answer the questions you have regarding the water in your basement. There are also 2 other options: you could contact your local health district or your state water quality board. They should be able to answer your questions. If for some reason they can’t, they should be able to suggest a consultant who can. Our expertise is in being able to identify and quantify what’s in a sample, not specifically how it got there.


    Thank you Dee for your reply. Just two questions you may be able to answer.
    Do trihalomethanes evaporate quite quickly once released into air?
    Can trihalomethanes be found in ordinary soil?

  22. Dee O'Neill, Columbia Analytical Says:

    Hello George!

    From the results you posted to us, there’s one THM in the water – trichloromethane at 0.21 ug/L. This would suggest that the water could be tap water. Has the local water company tested their leakage rate in your area against historic numbers? That might help determine where the water is coming from. You may also want to contact a local environmental consultant. They are very knowledgeable about groundwater.

  23. Darrell Says:

    I just received a letter today from the community water authority a stating
    that the averages for 2008 were:
    trihalomethanes: 145 ppb (1.8 x standard for drinking water)
    haloacetic acids: 140 ppb. (2.3 x standard for drinking water)
    The letter stated this was not an immediate risk, and that I did not need to use an alternate water supply. Is this true, or an amount that I should worry about?

  24. Dee O'Neill, Columbia Analytical Says:

    Hello Darrel,

    You can work your local health provider to help answer this question. As a laboratory, we can only provide information about what is in a sample.

    You might also be able to get additional information from your water company about their plans to address the issue.

  25. Vanessa Says:

    What are some side effects to drinking to water for a long period of time.

  26. Dee O'Neill, Columbia Analytical Services Says:

    For a complete list of possible effects of long-term ingestion of water containing trihalomethanes I suggest that you search the Center for Disease Control (CDC) or the EPA’s website. They should have the most up-to-date information on the effect of trihalomethanes on human health.

  27. Benjamin Says:

    Wow, what a lot of great information here. I stumbled upon your site while doing some research on a home water distiller. I’ve built a homemeade unit from a sealable crock pot, stainless steel tubing and some ?vinyl? flexible hose (from a homebrew kit) submerssed in a cool bath as the condenser. The first sample I pulled (the first 300 ml or so) tasted awful! Not just like bland, or flat water, but very sour/bitter…to the point that I think it’s not just pure water in there. I’m trying to figure out why the first sample would taste so bad (almost poisenous) and after reading a few articles about VOC’s and Trihalomethanes, I am now thinking maybe the Trihalomethanes boiled off first and then recondensed into a more pure and concentrated form. I’ve checked my annual water quality report (CCR) and found the TTHM’s level at 5.7 ppb. If 80 ppb is the “limit” then 5.7 ppb would be considered low – correct? Coud this kind of VOC be what I am tasting in the first small sample of my distilled water?

  28. Dee O'Neill, Columbia Analytical Services Says:

    I don’t know. There are many, many causes of sour/bitter tastes in water and they could come from any or none of the components of the system you’ve described. You would probably need to have the water tested to find out. You may want to talk to a experienced drinking water sampler to find out the best way to isolate the different components of your system, if needed. I’m not sure TTHMs at 5.7 ppb can be discerned by taste.

  29. TIM Says:

    Would trace amounts of xylene in water raise THM levels

  30. Dee O'Neill, Columbia Analytical Services Says:

    We don’t have any data about the effects of trace amounts of xlyene on THM levels.

  31. chemist sayed Says:

    hi , I’m going to begin my master degree on trihalomethanes , please, could u suggest some points i may focus on during my research , ii’m working in a ref. lab. of water quality , and work on GC ECD instrument .

    tahnks alot

  32. Dee O'Neill, Columbia Analytical Services Says:

    There are many aspects that might interest you. I would suggest that you review the EPA and CDC websites about THMs and see what avenues for research are the most appealing. Good luck with your studies!

  33. Sharon Garvin Says:

    For at least the past 18 years the water here has always been about 0.080. Our water company sends out notices several times a year informing us that the TTHM’s are still at the same level. We have paid a large amount for new water equipment and still nothing really has changed.
    The letter always tells us that drinking this water for an extended period of time can cause, liver, kidney, or central nervous system and may increased risk of getting cancer. The rate of cancer here in our little town of mainly retired people is staggering. Myself included, I have severe kidney and some liver problems. My husband has had cancer and also endocarditis. They never found the bacteria type and still don’t know what caused this. He had to have open heart surgery at the age of 83. Can you tell me why the risk is ignored since we all have lived here and drank this water for many years. I don’t know who to believe. Thanks for your help

  34. Dee O'Neill, Columbia Analytical Services Says:

    Hello! I am very sorry to hear of all your health problems and concerns. The questions you ask would be better posed to your drinking water provider and local health officials, as they are the proper persons to address these issues.


    Hi Dee,
    I wrote to you sometime ago about the presence of trichloromethane in water running into my basement.
    I carried out 3 analysis and the results are as follows: 1st analysis:0.21ug/l , 2nd analysis: 4ug/l , 3rd analysis : 1ug/l
    However the DIbromochloromethane and Dichlorobromomethane levels are below detectable levels in all 3 analysis. Are there any reasons for these THM’s to be absent while Trichloromethane is present and could the absence of Bromo’s from the analysis lead to a conclusion that the water is ground water rather than treated water?

  36. Dee O'Neill, Columbia Analytical Says:

    Hello George!

    There are a number of scenarios that could explain your results. We recommend you contact an environmental engineering consultant. As a laboratory, we attest to the manner and validity of the data we ourselves produce.

    Thank you and good luck!

  37. Tokunbo Awofisayo Says:

    What is the best method for testing for the residual chlorine in drinking water beside instrumental method

  38. Columbia Analytical Says:

    Hello Tukunbo!

    I suggest you contact your drinking water regulatory agency to see what non-instrument methods they allow.

  39. greg simmons Says:

    In a water distribution system,where are tthms likely to be found at higher levels?

  40. greg simmons Says:

    In a water distribution system,where are HAA5′s likely to be found at higher levels?

  41. Columbia Analytical Says:

    Hello Greg,

    In respect to both questions above, it really depends on the design of your distribution system. You should contact your state drinking water agency. They should be able to review your system and tell you the most likely locations for higher build ups, if at all.

  42. greg simmons Says:

    Name several ways in which to lower TTHM &HAA5 levels in a distribution system.

  43. Columbia Analytical Says:

    Hi Greg,

    Your question really depends on your system’s needs to use a disinfectant to kill bacteria and viruses that can cause serious health effects. Your state drinking water agency can give you recommendation about how to keep the levels of HAAs and TTHMs low. There also may be alternatives to the use of chlorine that you could explore.

  44. mehraban Says:

    I have a question about THMs measurement in drinking water. I want to now is it possible by HPLC method? thank you

  45. Dee O'Neill, Columbia Analytical Services Says:

    Hello! The method we use is the only one currently approved for TTHM in drinking water and that is EPA Method 524.2.

  46. Anthony Says:

    Of the samples that you have tested, what is the chlorine disinfection method that you find to have the TTHM and HAA5 issues? I had thought that Chloromine disinfection is the larger contributor as compared to break-point chlorination. If higher THM’s are produced by break-point chlorination, could you please give an explanation as to how and maybe a why?

    PS. Have you tested any swimming pool water for THM’s? What have you experienced?

    PPS. George have you thought about converting the basement into a swimming pool?? Just joking. I hope your problems are fixed. It’s a good thing your problem is not a broken sewer pipe.

    Tango Mike

  47. Dee O'Neill Says:

    Hi Tango Mike,

    Chlorine is used extensively as a primary disinfectant because of its ability to kill bacteria, viruses and other harmful organisms relatively quickly. Chlorine is very reactive (chemically “unstable”) and will kill organisms and, also, form chloramines when ammonia is present in water. (usual in surface waters or waters influenced by surface waters). Chloramines are more chemically stable, and can kill organisms in water distribution pipes or those that survived the initial chlorination before the water reaches your home. They are considered to be longer acting that chlorine, but not as effective, which is why chloramines are used primarily as a secondary disinfectant in surface water systems. All water systems whose source(s) are from or under the influence of surface waters are also required to have certain residual levels of disinfectant in their distribution systems.

    So to answer your question – all chlorination/choramine treatment will cause disinfection by-products like TTHMs and HAAs to be formed. As to which one will cause more – that depends on the amount of disinfection agents used. However, the EPA has very strict regulations about how much TTHMs or HAAs are considered safe in drinking water in systems that use chlorination. Those allowable levels are explained quite thoroughly on the EPA’s safe drinking water website.

    Ground water systems are only required to disinfect as necessary (when bacteria, etc are detected) and are not required to have a detectable disinfectant residual in their distribution system.

    In our business we follow very strict confidentiality policies, so we do not talk about what what we have tested unless we have the express permission from our clients to discuss testing results. However, there is a lot of good information on the web concerning pools and chlorine/chloramines.

    Thank you for your questions.

  48. Monica Says:

    We recently got a notice in our water bill that our water tested at .083MG/L TTHM for the last four quarters. The letters also states that “the levels detected do not pose an immediate risk to your health, but people who drink this water over many years may experience problems with their liver, kidneys, or central nervous systems, and may have an increased risk of getting cancer. We are currently running our drinking water through a filter system. How can we get this water tested to see if it is working to take out the TTHM from the water? Is there a test kit we can get somewhere or something?

  49. Dee O'Neill Says:

    Hello Monica!

    We do not sell water filters so are not able to give you any information about them. I suggest you get information from the company that makes your system. they should be willing to give you results of water testing showing you what their system filters out. Most reputable filter system companies will also entertain testing your water after it goes through the filter system to ensure that it’s removing what they said it will remove. TTHMs are usually dealt with at the water provider level. Have you contacted your water supplier to find out what they are doing to address the situation? You could also contact your local health provider to see what they advise.

    Good luck!

  50. larry Says:

    Can you boil TTHMs from the water or is filtering the only way to remove them?

  51. Dee O'Neill Says:


    We are an analytical laboratory – we can tell you what’s in a sample. We’re not drinking water treatment experts and since treatment options can change very rapidly we suggest that you contact your local water service provider or local health department to find out what your options are.

    Good luck!

  52. Inimfon Udoetok Says:

    1. What constitutes residual chlorine in sewage water?
    2. Can compounds of chlorine like chloroamines, hypochlorite ions be detected as eresidual chlorine in sewage water?

  53. Jackie Says:

    What a wonderful resource you are! Our company just started disinfection this year due to the installation of a pressure stabilization tank, so this is my first year for DBP sampling. My State DOH has been very helpful, but have a question purely from curiosity…why must the sample being shipped to the Lab (we outsource, and must place our sample cooler in a Courier box) be kept at a temp of 3 to -6 degrees Celsius? I’m going to double bag some crushed ice to surround the samples in the cooler and pray that works…but how does temperature affect the analysis? Thanks!

  54. Zelani Says:


    I am looking for a spectrophotometer method to determine free chlorine in water. All the methods I could find is for specific instruments that has an existing calibration. Agents selling DPD kits can only tell you how to use their instruments with existing calibrations. We do not want to spend money on a new instrument therefore need to do a calibration on our instrument. Can you help?

    Thank you

  55. admin Says:

    Hi Zelani,

    I suggest that you contact the manufacturer of your spectrophotometer for a method to calibrate it.


    Dee O’Neill
    Columbia Analytical Services, Inc.

  56. Susan Says:

    Boiling the water will work to remove the THMs since they are volatile (this also has the added benefit of inactivating and/or killing potential biological pathogens in the water) but remember to turn the hood on over the stove so they are released into the atmosphere and the harmful effects are minimized due to dilution.

  57. timothy Q. Says:

    Hello sir. I need to find out if TTHM has any effects to calcium depositing in humans system.

  58. admin Says:

    Hi Timothy,

    Thank you for contacting us! We suggest your contact your local health care provider with your question, as they should be able to better assist you.

    Thank you,

    ALS Environmental
    Formerly Columbia Analytical Services


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