Assessing the risk of lead exposure to children from drinking water in Metro Vancouver child care facilities
Bibliographic record
Abstract
Background: Environmental lead exposure has been a concern since the early 1970’s. With the reduction of airborne lead for inhalation, ingestion from food and water has become the major route of exposure leading to elevated blood lead levels. Previous research and the recent lead contamination of drinking water in Flint, Michigan demonstrate the vulnerability of young children and potential for exposure through drinking water. The purpose of this study was to assess and characterize the risk of lead contamination of drinking water for Metro Vancouver-area early childhood care facilities, and the effect of flushing fixtures as a control measure. Method: 91 drinking water samples were collected from various fixtures at 16 child care facilities at progressive time points to observe the effects of flushing and re-stagnation on total dissolved lead content. Analysis was performed using Varian AAS-240 coupled with GTA-120 graphite furnace atomic absorption spectroscopy. Results were analysed statistically using Excel 2010 and SAS/STAT® 14.2 software with SAS Studio 3.6 interface. Results: The mean (SD, min-max) lead concentrations of the water samples were 0.69 (2.32, 0.1-11.27) μg/L at zero minutes of flushing, 0.21 (0.44, 0.1-2.19) μg/L after one minute of flushing, 0.15 (0.17, 0.1- 0.87) μg/L after five minutes of flushing, 0.18 (0.17, 0.1 -0.64) μg/L after re-stagnation, and 0.31 (1.20, 0.1-11.27) μg/L overall. One outlier sample had a lead concentration of 11.27 μg/L, which exceeded Health Canada’s maximum allowable concentration of 10 μg/L. The decrease in mean lead concentration between zero minutes and one minute of flushing was statistically significant (p=0.0020). Conclusions: The results indicate that lead contamination of drinking water in child care facilities is present but below regulatory action levels under normal circumstances. The flushing of fixtures for at least one minute was shown to be effective in lowering lead concentrations further. Efforts should be taken to identify facilities at higher risk of lead contamination and to educate operators of flushing as an effective control measure.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".