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Exposure related observations in humans: other data

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Endpoint:
exposure-related observations in humans: other data
Type of information:
other: Incident publication
Adequacy of study:
supporting study
Study period:
No data
Reliability:
other: Exposure related observations
Rationale for reliability incl. deficiencies:
other: Publication underestimated the number of deaths in the exposed area and non¬exposed area, but this would not be large enough to invalidate the conclusions.
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
Retrospective study of mortality after a water pollution incident at Lowermoor in North Cornwall.
Author:
Owen PJ, Miles DPB, Draper GJ and Vincent TJ.
Year:
2002
Bibliographic source:
BMJ. 324 : 1189.

Materials and methods

Type of study / information:
Retrospective study was conducted to assess the mortality in relation to water pollution incident at Lowermoor in north Cornwall.
Endpoint addressed:
other: mortality
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
A cohort-retrospective study was conducted to assess the mortality in relation to water contaminated with aluminium sulphate.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report): Aluminium sulphate

Method

Ethical approval:
not applicable
Details on study design:
Twenty tonnes of aluminium sulphate were inadvertently emptied into the water supply at the Lowermoor treatment works in north Cornwall on 6 July 1988. The maximum recorded aluminium concentration was 620000 µg/L compared with the maximum concentration admissible at the time by the European Community of 200 µg/L (Rowland et al., 1990). Records of deaths in the population whose records were flagged between July 1988 and December 1997 were analysed. Mortality was compared in the area with water pollution (n=11114) with that in an adjacent area free of pollution (n=5359). It was also compared death rates with those in Cornwall and the Isles of Scilly, and England and Wales. Death rates for differences in age distribution and sex was corrected.
Exposure assessment:
estimated
Details on exposure:
TYPE OF EXPOSURE: Accidental exposure

TYPE OF EXPOSURE MEASUREMENT: Mortality

EXPOSURE LEVELS: 20 tonnes (maximum recorded aluminium concentration was 620000 µg/L)

Results and discussion

Results:
- The ratio of the standardised mortality ratios (standardised to England and Wales) for the exposed and unexposed cohorts was 1.08 (95 % confidence interval 0.97 to 1.21); the exposed group had higher mortality, but the excess was not statistically significant. Compared with deaths in Cornwall as a whole, the number of deaths in the exposed group was lower than expected each year: fewer than expected died in the exposed group. The standardised mortality ratio for the exposed population for 1988­97 was 81.6 (77.2 to 86.2), using mortality rates for Cornwall as the standard, and 77.7 (73.5 to 82.0) with England and Wales as standard. For both standards of comparison, significantly fewer people died than expected.
- No statistically significant difference in deaths between the cohort exposed to aluminium sulphate in their water and the non­exposed cohort. The cohort exposed to the pollution had significantly lower mortality than the population of Cornwall and that of England and Wales. This may be because the area has generally low levels of deprivation and historically low death rates.

Any other information on results incl. tables

Table 7.10.5/1: Standardised mortality rates (95% confidence intervals) in groups exposed and unexposed to aluminium sulphate pollution after incident at Lowermoor, North Cornwall

 

Standard

Exposed population (E)

Unexposed

population (U)

Ratio (E/U) (95% CI)

England and Wales

77.7 (73.5 to 82.0)

71.8 (65.4 to 78.4)

1.08 (0.97 to1.21)

Cornwall and Isles of Scilly

81.6 (77.2 to 86.2)

75.9 (69.2 to 83.1)

1.07 (0.97 to 1.20)

Applicant's summary and conclusion

Conclusions:
No statistically significant difference in deaths between the cohort exposed to aluminium sulphate in their water and the non­exposed cohort.
Executive summary:

A cohort-retrospective study was conducted to assess the mortality in relation to water contaminated with aluminium sulphate.

 

Twenty tonnes of aluminium sulphate were inadvertently emptied into the water supply at the Lowermoor treatment works in north Cornwall on 6 July 1988.  Records of deaths in the population whose records were flagged between July 1988 and December 1997 were analysed. Mortality was compared in the area with water pollution (n=11114) with that in an adjacent area free of pollution (n=5359). It was also compared death rates with those in Cornwall and the Isles of Scilly, and England and Wales. Death rates for differences in age distribution and sex was corrected.

The ratio of the standardised mortality ratios (standardised to England and Wales) for the exposed and unexposed cohorts was 1.08 (95 % confidence interval 0.97 to 1.21); the exposed group had higher mortality, but the excess was not statistically significant. Compared with deaths in Cornwall as a whole, the number of deaths in the exposed group was lower than expected each year: fewer than expected died in the exposed group. The standardised mortality ratio for the exposed population for 1988­97 was 81.6 (77.2 to 86.2), using mortality rates for Cornwall as the standard, and 77.7 (73.5 to 82.0) with England and Wales as standard. For both standards of comparison, significantly fewer people died than expected. No statistically significant difference in deaths between the cohort exposed to aluminium sulphate in their water and the non­exposed cohort. The cohort exposed to the pollution had significantly lower mortality than the population of Cornwall and that of England and Wales. This may be because the area has generally low levels of deprivation and historically low death rates.