Copper sulphate

Direct observations: clinical cases, poisoning incidents and other

Administrative data

Endpoint:

direct observations: clinical cases, poisoning incidents and other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Already evaluated by the Competent Authorities for Biocides and Existing Substance Regulations.

Data source

Reference

Reference Type:

publication

Title:

Copper in infant nutrition: safety of World Health Organization provisional guideline value for copper content of drinking water.

Author:

Olivares, M., Pizarro, F., Speisky, H., Lönnerdal, B., and Uauy, R. (1998).

Year:

1996

Bibliographic source:

J Pediatr Gastroenterol Nutr, 26(3):251-257.

Materials and methods

Study type:

study with volunteers

Test guideline

Qualifier:

no guideline available

Deviations:

not applicable

Principles of method if other than guideline:

Not a guideline study.
The purpose of this study was to determine the biologic significance of chronic exposure of infants to drinking water with a copper content ranging
from less than 1.57 (<0.1 mg/l) to 31.48 µmol/l (2 mg/l).

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Cu2+

IUPAC Name:

Cu2+

Details on test material:

See Other information on Materials and Methods.

Method

Type of population:

other: Infants

Ethical approval:

confirmed and informed consent free of coercion received

Remarks:

The informed consent of parents was obtained before inclusion of an infant in the study, and the protocol was approved by the Ethics of Human Research Committee of the Institute of Nutrition and Food Technology of the University of Chile

Route of exposure:

oral

Reason of exposure:

other: drinking water

Exposure assessment:

estimated

Details on exposure:

See Other information on Materials and Methods.

Examinations:

See Other information on Materials and Methods.

Medical treatment:

See Other information on Materials and Methods.

Results and discussion

Clinical signs:

See Other information on Results.

Results of examinations:

See Other information on Results.

Effectivity of medical treatment:

See Other information on Results.

Outcome of incidence:

See Other information on Results.

Any other information on results incl. tables

Results

General characteristics of the groups were similar (see Table 1). The sex distribution was comparable, with a slight predominance of boys. There were no differences in birth weight among the studied groups. The socioeconomic level was the same.

Thirty-nine infants were withdrawn during the follow up: 17 (30.4%) in group I (blood sampling refusal = 8, protocol transgression = 4, change of address = 5); 3 (11.1%) in group II (blood sampling refusal = 2, change of address = 1); 13 (48.1%) in group III (blood sampling refusal = 10, protocol transgression = 1, change of address = 2); and 6 (28.6%) in group IV (blood sampling refusal = 4, change of address = 2).

Copper provided by foods, milk formula, and water used in the preparation of the formula was considered to calculate actual copper intake. However, it was not possible to include copper provided by breast milk because breast milk was not assayed for copper.

Formula-fed infants given drinking water with a high copper content received 2.3 ± 0.8 mg/day (318.7 ± 107.3 µg/kg per day) of copper at 4 to 6 months of age; 2.5 ± 0.7 mg/day (304.9 ± 84.5µg/kg per day) at 6 to 9 months, and 2.4 ± 0.7 mg/day (248.1 ± 84.0 µg/kg per day) at 9 to 12 months. The corresponding figures for formula-fed infants who received drinking water with a low copper content were 0.8 ± 0.5 mg/day (122.7 ± 107.4 µg/kg per day), 1.2 ± 0.7 mg/day (157.8 ± 146.0 µg/kg per day), and 1.2 ± 0.7 mg/day (128.6 ± 113.1 µg/kg day).

Breast-fed infants given drinking water with a high copper content, excluding that derived from breast milk, received 0.1 ± 0.2 mg/day (52.2 ± 48.5 µg/kg per day) of copper at 4 to 6 months of age; 1.5 ± 1.1 mg/day (179.0 ± 105.2 µg/kg per day) at 6 to 9 months, and 2 ± 1.1 mg/day (178.7 ± 82.1 µg/kg per day) at 9 to 12 months. The corresponding figures for breast-fed infants who received drinking water with a low copper content were 0.1 ± 0.2 mg/day (37.8 ± 36.7 µg/kg per day), 0.8 ± 0.7 mg/day (127.8 ± 126.2 µg/kg per day), and 1.6 ± 1.3 mg/day (174.1 ± 139.8 µg/kg per day).

There were no differences in growth and morbidity episodes among the four groups of studied infants (see Table 2). However, breast-fed infants had a significantly lower incidence of diarrheal episodes than did formula-fed infants during the 9 months of observation.

There were no differences in copper status among the four groups of infants at 6, 9, and 12 months of age (see Table 3 and Table 4). There were significant differences in serum copper concentrations between formula-fed and breast-fed groups at 6 months of age (28.3 ± 7.2µmol/l vs. 24.9 ± 7.9 µmol/l; F = 4.6552; p = 0.0369) and in erythrocyte metallothionein levels at 12 months of age (21.9 ± 7.0 Ug/Hb vs. 26.8 ± 7.5 Ug/Hb; F = 7.4909;p = 0.008). A significant difference in ceruloplasmin activity at 9 months was found between subjects who received drinking water with and without copper (350 ± 85 mg/l vs. 322 ± 75 mg/l; F = 5.4222;p = 0.0229). In addition, there were significant differences for this parameter in the breast-fed groups between infants who received drinking water with high and low copper content (t = 2.2295; p = 0.0032).

At 6, 9, and 12 months of age, the four groups of infants did not have significantly different findings in liver function tests (see Table 5). However, findings in formula-fed subjects differed significantly from this in breast-fed infants in total bilirubin at 6 months of age (2.22 ± 1.18 µmol/l vs. 2.80 ± 1.23 µmol/l;F = 5.3684; p = 0.025) and in serum glutamic oxaloacetic transaminase at 9 months of age (0.29 ± 0.09 µkat/l vs. 0.35 ± 0.14 µkat/l; F = 4.7111; p = 0.0326).

Discussion

There were no adverse effects associated with the consumption of water with a content of copper of 31.48 µmol/l (the WHO limit). None of the infants had acute or chronic symptoms or signs of toxicity, nor was a significant change in liver function noted. However, it is possible that the higher withdrawal rate of infants (mainly because of refusal of venous blood sampling) in the groups who received drinking water with a copper content of 31.48 µmol/l could be the consequence of a higher prevalence of unreported symptoms of intolerance.

Serum copper and ceruloplasmin concentrations and superoxide dismutase activity are typically used to assess copper status. It is well known that serum copper and ceruloplasmin concentrations decrease during moderate to severe copper deficiency, whereas superoxide dismutase activity is more sensitive to marginal copper deficiency. Although these laboratory parameters are not currently used to evaluate copper overload, and although they may not be the most suitable or sensitive markers to assess the excess presence of copper, they are the only noninvasive tools for use in healthy infants. Ideally, measurements of hepatic copper stores should be conducted, but again, there are no noninvasive methods to assess hepatic copper content. Because most of the hepatocellular copper is stored bound to metallothionein and copper overload induces metallothionein, increasing its copper saturation in liver, the use of metallothionein as a possible indicator of copper burden was explored. However, no differences were found in erythrocyte metallothionein between groups, with and without extra copper in water. No other data are available of the correlation of metallothionein and copper concentrations.

The lack of major differences in copper status observed between infants who received water with low and high copper content may be explained in different ways. A first explanation is that these indexes are not sensitive enough to detect changes in infants with normal copper nutrition. It can be assumed that all children in this study had adequate copper intake, because they received solid foods and a milk formula that contained 7.87 µmol/l of copper, or breast milk. A second explanation is the adaptation to a high or low copper intake because of strong homeostatic regulation of copper absorption and excretion.

Applicant's summary and conclusion

Conclusions:

No acute or chronic adverse consequences of consuming water with copper content of 31.48 μmol/l (2 mg/l) were detected in infants during the first year of life. The results support the safety of the World Health Organization's provisional guideline value for copper in drinking water during infancy.

Executive summary:

Background

Copper is an essential nutrient for humans. Recently, a limit of 31.48μmol/l (2 mg/l) was proposed by the World Health Organization as the provisional guideline value for copper content of drinking water. The objective of the study was to determine the tolerance of chronic exposure to drinking water with low or high copper content in infants.

Method

Healthy infants (n = 128) were randomly assigned to receive drinking water with less than 1.57 μmol/l (< 0.1 mg/l) (n = 48) or 31.48 μmol/l (2 mg/l) of copper (n = 80) from 3 to 12 months of age. At 6, 9, and 12 months of age, serum concentrations of copper, ceruloplasmin, and superoxide dismutase; erythrocyte metallothionein; bilirubin; transaminases; and F-glutamyl transferase were measured.

Results

Small differences in biochemical indexes of copper nutrition were observed between the groups, but there was no evidence of adverse or toxic effects. These findings may be explained by an adaptive response to the higher copper intake, limiting copper absorption, and increasing biliary secretion, as well as by an increase in copper storage. It is also possible that the sensitivity of the biochemical indicators employed to detect differences in copper status is limited.