VALIDATING URINARY TRICHLOROACETIC ACID AS A BIOMARKER OF EXPOSURE FOR DISINFECTION BYPRODUCTS IN DRINKING WATER-A THIRD HUMAN TRIAL
Bibliographic record
Abstract
Epidemiologic evidence of disinfection by-products (DBPs) causing adverse human health effects needs improved assessment of individual drinking water exposure to DBPs. Development of a feasible biomarker offers an approach to this need. Trichloroacetic acid (TCAA) in urine was confirmed to have sufficiently long retention (urinary excretion half lives from two to six days) in two previous human exposure pilot trials (ten participants in Adelaide, Australia and five participants in Edmonton, Canada) to make urinary TCAA a promising candidate as a biomarker. The current pilot study is to verify our protocol for performing a larger scale human exposure trial (∼50 participants) to ultimately validate urinary TCAA as a biomarker of non-volatile DBP exposure via drinking water. In December 2002, we recruited sixteen healthy women of reproductive age to participate in this study. Following an initial telephone interview, ten eligible volunteers were selected to obtain demographic data, patterns of food, beverage and water consumption, and set up schedules' for water delivery and blood and urine sample collections. The current pilot trial follows previous successful experience with the second (Edmonton) trial, where TCAA exposure was achieved by using the public water supply from another large Canadian city. This supply has sufficient TCAA to allow for ready detection of TCAA in urine following drinking water consumption. Ultimately, ten volunteers will be randomly assigned into each of five exposure groups using this municipal tap water source, diluted with TCAA-free bottled water to achieve tapwater concentrations of 0%, 12.5%, 25%, 50% and 100%, respectively. Each participant is provided details of the study design and provides informed consent prior to participation. The current pilot study of eight participants is being performed to verify the feasibility of all of the logistics of the protocol for the large study cohort of fifty. The total exposure period is 15 days. The first urine morning samples are collected on days 1, 2, 8, 14, 15 and 16 immediately after tap water consumption. Whole blood samples are collected on days 1, 8, 14 and 15. TCAA and chloral hydrate (CH) are analyzed in all urine and whole blood samples as well as in tap water samples from each exposure group. Serum and urine samples are collected for measurement of creatinine in order to correct for variation of urinary volume. The TCAA analytical methodology is performed by liquid-liquid microextraction (LLME), head-space solid phase microextraction (SPME), gas chromatography (GC) and electron capture detector (ECD). Liquid-liquid extraction (LLE), GC and ECD methods are used for the analysis of THMs (trihalomethane), HANs (haloacetonitrile), HKs (haloketone), CH (chloral hydrate) and CP (chloropicrin). The pilot trial has functioned well and the analytical data are being reviewed to determine the most appropriate dilution levels for the main study. The pilot study population of ten participants provides a reasonable basis for evaluating the practical problems inevitably experienced with an ambitious experiment with human volunteers. This study protocol appears to provide a practical and viable approach to validating urinary TCAA as a biomarker of non-volatile DBP exposure via drinking water.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".