A review of drinking water standards for copper and investigation of copper levels in drinking water in institutional buildings
Bibliographic record
Abstract
Copper (Cu) has been used for centuries in the house, in industry and in agriculture. As a transition metal, it can adopt distinct redox states, which allows it to function as a catalytic cofactor in many enzymatic reactions essential to living organisms. Although copper is an essential nutrient, elevated levels of copper can be toxic. Indian Childhood Cirrhosis is a well-known epidemic of copper toxicity. Once recognized as a public health concern, daily recommended intakes were assessed at 0.3 to 3.0 mg/day for adults and at 0.1 to 2.0 mg/day for infants and young children, while the maximum safe levels for adults ranges from 0.8 to 30 mg/day and cannot be determined, due to insufficient data, for infants and young children.One of the main sources of copper ingestion is drinking water due to the extensive use of copper pipes for plumbing, although copper is more often recognized as an aesthetic concern rather than a health concern. Many countries, including Canada, have not yet established health-based drinking water standards for copper. Currently, the WHO has the most referenced health-based guideline value for copper at 2 mg/L. However, the supporting evidence for this guideline value has been questioned due to high uncertainty, insufficient data and questionable interpretation of data. Exposure studies for copper in drinking water have not considered ingestion at work or school, where the majority of waking time is spent, which may underestimate the associated health risks.First, the strength of the evidence and the science used to set the drinking water guideline values for copper is reviewed. Guideline levels, developed only for acute copper toxicity, rarely occur due to the low taste threshold of copper. There are irregularities in the reported levels of copper exposure for acute effects and the calculation of levels is not conservative. Second, copper concentrations have been measured in large institutional buildings to assess potential exposure levels. The results of the field study reveal that drinking water in these large buildings can provide a significant contribution to daily copper intakes ranging from 50% to almost 100% of the recommended daily intake values (0.7-0.8 mg Cu/day) proposed by the WHO. The field survey also shows that flushing in large building can reduce copper levels in the water by 40%. Lastly, the results confirm higher copper levels in newer or recently renovated buildings, likely due to the lack of time to develop a protective scale (due to oxidization of the copper) reducing dissolution of the pipes.
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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 | 0.005 | 0.010 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.010 | 0.012 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".