CONCLUSIONS OF THE RISK CHARACTERIZATIONBased on the weight of evidence from laboratory studies, field studies and the application of predictive models, the substitution of chlorine dioxide for elemental chlorine results in:
- Reduction in the quantities of organochlorines produced
- Reduction in the degree of chlorine substitution in the organochlorines produced
- Reduction in the degree of persistence of the organochlorines produced
- Reduction in the potential for bioaccumulation and food chain transfer
- Reduction in adverse ecological effects
- Reduction in risk of adverse ecological effects from organochlorines to insignificant levels
Based on the data available, mills bleaching with chlorine dioxide (100% substitution) and employing secondary treatment and with dilution typical of N. American mills, present an insignificant risk to the environment from organochlorine compounds. However, sufficient evidence exists from observations at non-bleached mills to suggest that other non-chlorinated compounds which are released or formed during the production of pulp may cause responses such as induction of P4501A and changes in hormone levels. The identification of these compounds and the elucidation of their mechanisms of action should be a priority.
This review is based on a report "A review and assessment of the ecological risks associated with the use of chlorine dioxide for the bleaching of pulp". Keith Solomon, Harold Bergman, Robert Huggett, Donald Mackay and Bruce McKague. October 1993 prepared for the Alliance for Environmental Technology.
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