Understanding Your Shower
Water Quality
Some water constituents can enter indoor air or contact skin during showering. The relevance depends on the water, the compound, the setting, and individual circumstances.
How Shower Water Quality Can Matter
Drinking, skin contact, and inhalation can all be relevant routes for some substances. Their relative importance depends on the contaminant and the circumstances.
The Science of Shower Exposure
Research published in the American Journal of Public Health examined uptake of volatile compounds during bathing. Studies of this kind show that inhalation and skin contact can contribute to exposure; their findings depend on the compounds and conditions studied and do not establish a universal comparison with drinking water.
Research has measured trihalomethanes in bathroom air during and after showering. Air levels and exposure vary with water composition, temperature, ventilation, and other conditions; a general equivalence with drinking a particular volume of water cannot be inferred.
What's in Your Shower Water?
Tap each contaminant card to see scientific details, data points, and health effects specific to shower and bath exposure.
Chlorine & Chloramine
Exposure variesShowering can involve contact with water and, depending on conditions, airborne byproducts
Trihalomethanes (THMs)
Exposure variesSome disinfection byproducts can move from water into indoor air during a shower
Hard Water Minerals
Household effects varyHardness minerals can contribute to scale and affect soap performance
Volatile Organic Compounds (VOCs)
Depends on sourceSome volatile compounds can pass from water into indoor air
Heavy Metals
Check source waterHot water may draw more metals from plumbing; use cold water for drinking and cooking
Bacteria & Biofilm
Depends on settingBiofilm can develop in showerheads and plumbing; the organisms and potential relevance vary
How Temperature Affects Your Exposure
Temperature can affect volatilization for some compounds. These general labels are not exposure measurements or individual risk ratings; results depend on water chemistry and conditions.
Cool water
Warm water
Hot water
Very hot water
Water Characteristics, Skin & Hair
Water characteristics may affect comfort for some people, but they do not diagnose or explain a skin or hair condition.
Eczema / Atopic Dermatitis
Water is one of many possible factorsResearch has examined possible associations between water hardness and eczema, but an association does not show that household water causes a person's condition.
Psoriasis
Symptoms and triggers varySkin irritation has many possible triggers. Evidence here does not establish that chlorine or hardness causes psoriasis or that a shower filter treats it.
Contact Dermatitis
Many possible causesContact dermatitis can result from many exposures. A water-quality result alone cannot diagnose its cause.
Dry Skin & Hair Damage
Experiences varyHardness can affect lathering and mineral residue. Claims about hair or skin effects vary, and water hardness alone does not establish a health problem.
What the Studies Say
Chlorine Absorption During Bathing
American Journal of Public Health, 1984
Early research measured chloroform uptake during showering and bathing, including changes in blood levels after exposure. The findings concern the study conditions and do not establish a fixed shower-to-drinking equivalence for people generally.
THM Inhalation Exposure from Showering
Environmental Health Perspectives, 2007
This study measured total trihalomethane (TTHM) concentrations in bathroom air during and after showering. It reported changes in air levels over the study period; the measured concentrations depend on the study setup and should not be treated as a universal exposure estimate.
Hard Water and Eczema Prevalence
Journal of Allergy and Clinical Immunology, 2017
This research examined an association between water hardness and eczema in children. An observed association does not show that hardness caused eczema or predict an individual's risk.
Showerhead Biofilm & NTM Bacteria
Proceedings of the National Academy of Sciences, 2018
Researchers analyzed biofilms from 656 household showerheads across the U.S. and Europe and reported enriched populations of Mycobacterium species (NTM). The geographic correlation reported in the study does not show that a showerhead caused disease in an individual.
Find Out What's in Your Shower Water
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