Why use Shower Filters? A summary of available studies.

 Shower filters can be fitted in seconds and are one of the most effective ways to reduce your exposure to chlorine (and disinfection by-products), fluoride and other chemicals. There have been several studies which have attempted to understand the effects of inhalation of chlorine gas through the lungs and absorption of chemicals through the skin and the associated health impact.  In this blog, we summarise the findings.According to the Centre for Research in Environmental Epidemiology:“THM and Health Effects We must explain that all compounds formed in the process water disinfection by-products are collectively called disinfection byproducts (DPB). Trihalomethanes (THMs) are a group of disinfection byproducts formed when chlorine is used as a disinfectant. THMs majority found in drinking water are chloroform, bromodichloromethane (BDCM), the dibromochloromethane (DBCM) and bromoform.Epidemiological studies associate with certain exposures in trihalomethanes (THM) and, in general, exposure to disinfection byproducts with health effects such as bladder cancer. Studies of bladder cancer find an increased risk due to long exposure to THMs (30 years) although the results are not always significant. The International Agency for Research on Cancer (IARC) classifies chloroform and bromodichlorometane as possibly carcinogenic to humans under certain exposure conditions. This means that although there is evidence of carcinogenicity in experimental animals, the evidence is limited in humans. Bromoform and dibromochlorometane not classified as carcinogens. “(1)Epidemiological studies have looked at the associations between exposure to DBPs in drinking water with cancers, adverse birth outcomes and birth defects. Meta-analyses and pooled analyses of these studies have demonstrated consistent associations for bladder cancer (2) (3) and for babies being born small for gestational age, (4) but not for congenital anomalies (birth defects).(5) Early-term miscarriages have also been reported in some studies. (6) (7) The exact putative agent remains unknown, however, in the epidemiological studies since the number of DBPs in a water sample are high and exposure surrogates such as monitoring data of a specific by-product (often total trihalomethanes) are used in lieu of more detailed exposure assessment. The World Health Organization has stated that "the risk of death from pathogens is at least 100 to 1000 times greater than the risk of cancer from disinfection by-products (DBPs)" {and} the "risk of illness from pathogens is at least 10 000 to 1 million times greater than the risk of cancer from DBPs". (8)With regard to the effect of chlorine and DPBs on the skin, according to the study “Interactions between domestic water hardness, infant swimming and atopy in the development of childhood eczema.” (Chaumont A, Voisin C, Sardella A, Bernard A.) at the Louvain Centre for Toxicology and Applied Pharmacology, Faculty of Medicine, Catholic University of Louvain, Brussels, Belgium:“Our study shows that exposure to hard water and infant swimming interact with atopic status to increase the prevalence of childhood eczema. A breaching of the epidermal barrier by detergents or salts in hard water and by chlorine-based oxidants in swimming pool water might explain these interactions.” (9)With regard to water hardness, according to the study “Atopic eczema and domestic water hardness” (McNally NJ, Williams HC, Phillips DR, Smallman-Raynor M, Lewis S, Venn A, Britton J. Health Research Group, Department of Geography, University of Nottingham, University Park, UK:“Exposure to hard water in the home may increase the risk of eczema in children of primary-school age” (10)According to the British Water Fact Sheet:“Over the years, many eczema sufferers have reported that the use of softened water has substantially reduced inflammation. Softened water is also known to have a calming, soothing effect on other skin problems, including psoriasis, but such benefits have not been formally established, although recent research by a leading UK dermatologist identified a strong link between hard water and childhood eczema.”In the American Journal of Public Health, Halina Szejnwlad Brown, Donna Bishop and Carol Rowan contrast their estimates of skin absorption versus drinking for three toxic chemicals: Toluene, Ethylbenzene, and Styrene. Depending both on the compound involved and the body region exposed, skin can act as a fairly strong barrier to chemical entry or as no barrier at all. Their analyses were based on data published for the hand, one of the least porous areas of the body. Their finding was that for a swimmer, between 83 percent and 91 percent of the chemicals entering the body came through the skin. (12)“Assessments of drinking water safety rely on the assumption that ingestion represents the principal route of exposure. A review of the experimental literature revealed that skin penetration rates for solvents are remarkably high, and that the stratum corneum is a less effective barrier to penetration than traditionally assumed.We conclude that skin absorption of contaminants in drinking water has been underestimated and that ingestion may not constitute the sole or even primary route of exposure. “ (12)In the study “Chlorination of Drinking Water and Cancer Incidence in Norway” by Flaten T P (Department of Chemistry, College of Arts and Science, The University of Trondheim, Trondheim, Norway).“On two geographical levels (counties and municipalities), both for men and women, chlorination of drinking water was associated with an increased incidence of cancer of the colon and rectum. After adjusting for potential confounding variables, also measured on a geographical basis, the associations were still significant at the county level (adjusted for population density, income, education, fat and fibre intake etc.), but not at the municipality level. The observed associations are weak, chlorination being associated with a 20–40% increase in colorectal cancer rates. Due to inherent methodological limitations in ecological studies like the present one, causal interpretations should be made with great care. Thus, although the results give some support to the hypothesis that drinking water chlorination is associated with colorectal cancer, they do not provide strong evidence of a causal relationship.”A follow on study entitled “Drinking water chlorination and cancer – a historical cohort study in Finland”  (Meri Koivusalo, Eero Pukkala, Terttu Vartiainen, Jouni J.K. Jaakkola, and Timo Hakulinen) concluded:“Chlorination of water rich in organic material is known to produce a complex mixture of organochlorine compounds, including mutagenic and carcinogenic substances. A historical cohort study of 621,431 persons living in 56 towns in Finland was conducted in order to assess the relation between historical exposure to drinking water mutagenicity and cancer. Exposure to quantity of mutagenicity was calculated on the basis of historical information of raw water quality and water treatment practices using an empirical equation relating mutagenicity and raw water pH,KMnO4 value and chlorine dose. Cancer cases were derived from the population-based Finnish Cancer Registry and follow-up time in the study started in 1970. Age, gender, time period, social class, and urban residence were taken into account inPoisson regression analysis of the observed numbers of cases using expected numbers of cases standardized for age and gender as a basis. Excess risks were calculated using a continuous variable for mutagenicity for 3,000 net rev/l exposure representing an average exposure in a town using chlorinated surface water. After adjustment for confounding, a statistically significant excess risk was observed for women in cancers of the bladder (relative risk [RR] = 1.48, 95 percent confidence interval [CI] = 1.01-2.18), rectum(RR = 1.38, CI = 1.03-1.85), esophagus (RR = 1.90,CI = 1.02-3.52), and breast (RR = 1.11, CI = 1.01-1.22). These results support the magnitude of excess risks for rectal and bladder cancers found in earlier epidemiologic studies on chlorination by-products and give additional information on exposure response concerning themutagenic compounds. Nevertheless, due to the public health importance of water chlorination, uncertainty related to the magnitude of observed risks, and the fact that excess risks were observed only for women, the results of the study should be interpreted with caution.”  (13)According to the study entitled “Exposure estimates to disinfection by-products of chlorinated drinking water.”  In the Journal of Environmental Health Perspectives (C P Weisel, H Kim, P Haltmeier, and J B Klotz) evidence was collected which demonstrated inhalation of chlorine DPBs through the lungs:“Exposure to disinfection by-products (DBPs) of drinking water is multiroute and occurs in households serviced by municipal water treatment facilities that disinfect the water as a necessary step to halt the spread of waterborne infectious diseases. Biomarkers of the two most abundant groups of DBPs of chlorination, exhaled breath levels of trihalomethanes (THMs) and urinary levels of two haloacetic acids, were compared to exposure estimates calculated from in-home tap water concentrations and responses to a questionnaire related to water usage. Background THM breath concentrations were uniformly low. Strong relationships were identified between the THM breath concentrations collected after a shower and both the THM water concentration and the THM exposure from a shower, after adjusting for the post shower delay time in collecting the breath sample. Urinary haloacetic acid excretion rates were not correlated to water concentrations. Urinary trichloroacetic acid excretion rates were correlated with ingestion exposure, and that correlation was stronger in a subset of individuals who consumed beverages primarily within their home where the concentration measurements were made. No correlation was observed between an average 48-hr exposure estimate and the urinary dichloroacetic acid excretion rate, presumably because of its short biological half-life. Valid biomarkers were identified for DBP exposures, but the time between the exposure and sample collection should be considered to account for different metabolic rates among the DBPs. Further, using water concentration as an exposure estimate can introduce misclassification of exposure for DBPs whose primary route is ingestion due to the great variability in the amount of water ingested across a population”.(14)According to the study “Human health risk assessment from exposure to trihalomethanes in Canadian cities.” By Chowdhury S, Hall K.“Lifetime exposure to trihalomethanes (THMs) through ingestion, inhalation and dermal contacts may pose risks to human health. Current approaches may under predict THMs exposure by using THMs in cold water during showering and bathing. Warming of chlorinated water during showering may increase THMs formation through reactions between organics and residual chlorine, which can increase human health risks. In this study, THMs concentrations in shower water were estimated using THMs rate increase model. Using cold water THMs, exposure through ingestion was estimated, while THMs exposure during showering was estimated using THMs in warm water. Human health cancer risks and additional expenses for 20 most populated Canadian cities from exposure to THMs were estimated. Inhalation and dermal contact during showering contributed 30% to 50% of total cancer risks, while risks from inhalation and dermal contacts were comparable for all cities. Overall cancer risks were estimated between 7.2 x 10(-6) and 6.4 x 10(-5) for these cities. Cancer incidents were estimated highest for Montreal (94/year) followed by Toronto (53/year), which may require additional medical expenses of 18.8 and 10.7 million dollars/year for Montreal and Toronto respectively. Cancer risks from exposure to THMs can be controlled by reducing THMs in water supply and varying shower stall volume, shower duration and air exchange rate in shower stall.”“Chlorination for drinking water forms various disinfection by products(DBPs). Some DBPs are probably linked tohumancancer(e.g.,bladder,colorectalcancers)andotherchronicandsub-chroniceffects.This emphasizes the need to understand and characterize DBPs in drinking water and possible risks to human health. In this study, occurrences of DBPs throughout Canada were investigated. Trihalomethanes(THMs) were observed to be highest in Manitoba followed by NovaScotia and Saskatchewan, while haloacetic acids were highest in NovaScotia followed by Newfoundland and Labrador. Based on the characterization of DBPs, risk of cancer from exposure to THMs was predicted using ingestion ,inhalation and dermal contact pathways of exposure. In Canada, approximately 700 cancer cases may be caused by exposure to THMs in drinking water. Medical expenses associated with these cancer incidents are estimated at some $140 million/year. Expense may be highest in Ontario(∼$47 million/year)followed by Quebec(∼$25 million/year) due to a greater population base. This paper suggests improvements in water treatment, source protection and disinfection processes, and caution in the use of alternative disinfectants to reduce DBPs. Finally, elements are provided to mitigate risks and reduce cost estimates in future studies”(15)According to another study entitled “Risk from exposure to trihalomethanes during shower: probabilistic assessment and control.” By Chowdhury S, Champagne P.Exposure to trihalomethanes (THMs) through inhalation and dermal contact during showering and bathing may pose risks to human health. During showering and bathing, warm water (35 degrees C-45 degrees C) is generally used. Warming of chlorinated supply water may increase THMs formation through enhanced reactions between organics and residual chlorine. Exposure assessment using THMs concentrations in cold water may under-predict the possible risks to human health. In this study, THMs concentrations in warm water were estimated by developing a THMs formation rate model. Using THMs in warm water, cancer and non-cancer risks to human health were predicted for three major cities in Ontario (Canada). The parameters for risk assessments were characterized by statistical distributions. The total cancer risks from exposure to THMs during showering were predicted to be 7.6x10(-6), 6.3x10(-6) and 4.3x10(-6) for Ottawa, Hamilton and Toronto respectively. The cancer risks exceedance probabilities were estimated to be highest in Ottawa at different risk levels. The risks through inhalation exposure were found to be comparable (2.1x10(-6)-3.7x10(-6)) to those of the dermal contact (2.2x10(-6)-3.9x10(-6)) for the cities. This study predicted 36 cancer incidents from exposure to THMs during showering for these three cities, while Toronto contributed the highest number of possible cancer incidents (22), followed by Ottawa (10) and Hamilton (4). The sensitivity analyses showed that health risks could be controlled by varying shower stall volume and/or shower duration following the power law relationship. (16)According to another study entitled “Exposure to chlorination by-products from hot water uses.” By Weisel CP, Chen WJ:Exposures to chlorination by-products (CBP) within public water supplies are multiroute in water. Cold water is primarily used for ingestion while a mixture of cold water and hot water is used for showering, bathing others, dish washing, etc. These latter two activities result in inhalation and dermal exposure. Heating water was observed to change the concentration of various CBP. An increase in the trihalomethanes (THM) concentrations and a decrease in the haloacetonitriles and halopropanones concentration, though an initial rise in the concentration of dichloropropanone, were observed. The extent of the increase in the THM is dependent on the chlorine residual present. Therefore, estimates of total exposure to CBP from public water supplies need to consider any changes in their concentration with different water uses. The overall THM exposures calculated using the THM concentration in heated water were 50% higher than those calculated using the THM concentration present in cold water. The estimated lifetime cancer risk associated with exposure to THM in water during the shower is therefore underestimated by 50% if the concentration of THM in cold water is used in the risk assessment.References:(1)    Centre for Research in Environmental Epidemiology  http://www.creal.cat/en_noticies/view.php?ID=160(2)      Villanueva, C. M.; Cantor, K. P.; Grimalt, J. O.; Malats, N.; Silverman, D.; Tardon, A.; Garcia-Closas, R.; Serra, C. et al. (2006). "Bladder Cancer and Exposure to Water Disinfection By-Products through Ingestion, Bathing, Showering, and Swimming in Pools". American Journal of Epidemiology 165 (2): 148–56 http://pubs.acs.org/doi/abs/10.1021/es801169k(3)      Costet, N.; Villanueva, C. M.; Jaakkola, J. J. K.; Kogevinas, M.; Cantor, K. P.; King, W. D.; Lynch, C. F.; Nieuwenhuijsen, M. J. et al. (2011). "Water disinfection by-products and bladder cancer: is there a European specificity? A pooled and meta-analysis of European case-control studies". Occupational and Environmental Medicine 68 (5): 379–85http://oem.bmj.com/content/68/5/379(4)      Grellier, James; Bennett, James; Patelarou, Evridiki; Smith, Rachel B.; Toledano, Mireille B.; Rushton, Lesley; Briggs, David J.; Nieuwenhuijsen, Mark J. (2010). "Exposure to Disinfection By-products, Fetal Growth, and Prematurity". Epidemiology 21 (3): 300–13 http://www.ncbi.nlm.nih.gov/pubmed/20375841(5)      Nieuwenhuijsen, Mark; Martinez, David; Grellier, James; Bennett, James; Best, Nicky; Iszatt, Nina; Vrijheid, Martine; Toledano, Mireille B. (2009). "Chlorination, Disinfection Byproducts in Drinking Water and Congenital Anomalies: Review and Meta-Analyses". Environmental Health Perspectives: 1486–93 http://www.ncbi.nlm.nih.gov/pubmed/20019896(6)      Waller, Kirsten; Swan, Shanna H.; DeLorenze, Gerald; Hopkins, Barbara (1998). "Trihalomethanes in drinking water and spontaneous abortion". Epidemiology 9 (2): 134–140. http://www.ncbi.nlm.nih.gov/pubmed/9504280(7)      Savitz, David A.; Singer, Philip C.; Hartmann, Katherine E.; Herring, Amy H.; Weinberg, Howard S.; Makarushka, Christina; Hoffman, Caroline; Chan, Ronna et al. (2005). "Drinking Water Disinfection By-Products and Pregnancy Outcome". Denver, CO: Awwa Research Foundation.(8)      "Disinfectants and Disinfection By-Products Session Objectives [Water Sanitation Health (WSH)]". World Health Organization (WHO).(9)      “Interactions between domestic water hardness, infant swimming and atopy in the development of childhood eczema.” (Chaumont A, Voisin C, Sardella A, Bernard A.) http://www.ncbi.nlm.nih.gov/pubmed/22591883(10)   Atopic eczema and domestic water hardness” (McNally NJ, Williams HC, Phillips DR, Smallman-Raynor M, Lewis S, Venn A, Britton J. Health Research Group, Department of Geography, University of Nottingham, University Park, UKhttp://www.ncbi.nlm.nih.gov/pubmed/9716057(11)   British Water http://www.britishwater.co.uk/Data/Global/File/Fact%20Sheets/Fact%20Sheet%202.pdf(12)   The Role of Skin Absorption as a Route of Exposure for Volatile Organic Compounds (VOCs) in Drinking Water HALINA SZEJNWALD BROWN, PHD, DONNA R. BISHOP, MPH, AND CAROL A. ROWAN, MSPHhttp://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.74.5.479(13)   Oxford Journals Medicine International Journal of Epidemiology Volume 21,  Issue 1 Pp.  6-15.http://ije.oxfordjournals.org/content/21/1/6.abstract?sid=a800140c-886f-4c0f-8578-e25587431d4b & “Drinking water chlorination and cancer – a historical cohort study in Finland”  (Meri Koivusalo, Eero Pukkala, Terttu Vartiainen, Jouni J.K. Jaakkola, and Timo Hakulinen)(14)   Exposure estimates to disinfection by-products of chlorinated drinking water.”  In the Journal of Environmental Health Perspectives (C P Weisel, H Kim, P Haltmeier, and J B Klotz) - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1566339/(15)   Human health risk assessment from exposure to trihalomethanes in Canadian cities.” By Chowdhury S, Hall Khttp://www.ncbi.nlm.nih.gov/pubmed/20434775 & Disinfection by products in Canadian provinces: Associated cancer risk sand medical expenses(16)   Risk from exposure to trihalomethanes during shower: probabilistic assessment and control. By Chowdhury S, Champagne P. http://www.ncbi.nlm.nih.gov/pubmed/19131092(17)   “Exposure to chlorination by-products from hot water uses.” By Weisel CP, Chen WJhttp://www.ncbi.nlm.nih.gov/pubmed/8146396