Disinfection by-products

The text on this page is taken from an equivalent page of the IEHIAS-project.

• Trihalomethanes (THMs) and trichloroacetic acid (TCAA) may be used to measure human exposure to drinking water disinfection by-products.
• DBPs are formed through reactions between residual chlorine (and other halogen compounds) and natural organic materials such as fulvic and humic acids.
• THMs are volatile, while HAAs are classifies as non-volatile.

Disinfection by-products as biomarkers

Sample collection and storage

Matrix:

Most efforts have been concentrated on measuring THMs in blood and exhaled breath and HAAs in urine.

Kinetics:

• Uptake routes include ingestion, inhalation and dermal absorption.
• Contributions of different exposure routes to total uptake depends on which DBP is monitored.
• Generally HAAs are mainly taken up through drinking water
• THM uptake is through inhalation or ingestion from water.
• THMs have very short biological half-lives, only measurable in minutes following exposure.
• HAAs have longer biological half-lives, integrating exposure over several days.

Sampling conditions:

Blood and urine samples are gathered and stored using standard procedures. Exhaled alveolar air can be sampled in valved glass tubes, steel canisters or Tedlar air sampling bags

Sample measurement

Analytical aspects:

• Most methods combine gas chromatography and mass spectrometry techniques.
• Detection limits depend on the method, matrix and compound measured.
• General ranges of detection limit for DBPs in blood are < 1 pg/l - 0,1 mg/l (THMs) and > 1 ng/l (TCAA), 0,3-0,5 µg/l for TCAA in urine and 0,1-0,5 µg/m³ for THMs in exhaled alveolar air.

Performance characteristics:

Analytical reproducibility is generally good for THMs and TCAA in all matrices, with relative standard deviations of 2,8%-8,5%

Validation:

A number of standard methods for the measurement of DBPs is available from the USEPA

Confounding factors:

Age, sex, and occupational exposure may affect the observed DBP concentrations

Data interpretation

Concentrations reported in literature:

• Concentrations in water (shower, drinking, pool) are generally in the range of 10-50 µg/l, in shower and pool air between 10 and 200 µg/m³.
• Concentrations in exhaled air generally range from 4-54 µg/m³, plasma levels from 0,56-5,23 µg/l, and urine levels from 0-30 ng/min if excretion is followed in time

Dose-response/effect relationships:

No clear dose-response relationships are available

Time trend, geographical variation, susceptibel groups:

Children, frequent swimmers and occupationally exposed persons generally have higher risk of exposure