Page 973 - The Toxicology of Fishes

Case Study: Pulp and Paper Mill Impacts 953

Attempts to Identify the Causes of Impacts Associated with PMEs

Significant investments have been made by the pulp and paper industry in process control, bleaching
technology, and secondary effluent treatment which have greatly reduced but not removed environmental
effects (Munkittrick et al., 1998, 2002). It is important to note that the process changes implemented by
the pulp and paper industry during the 1990s have largely accomplished what they were designed to do:
to reduce acute toxicity, BOD, total suspended solids loadings, and discharges of organochlorine com-
pounds in effluent. The persistence in impacts on endocrine function is an observation that was first
noted in research conducted at a small number of mills (Munkittrick et al., 1992b, 1994) and has since
been validated on a national scale through analysis of EEM data (Lowell et al., 2004). In conducting
research projects at selected mills and in implementing the study designs on a national scale through
the EEM program, advances have been made in developing approaches for identification of stressors
that are responsible for the persistent effects (nutrient enrichment, reproductive changes) in fish (Dubé,
2004). Investigation-of-cause approaches generate information on effects at increasing degrees of reso-
lution with the goal of providing the information necessary for mitigation.
Hewitt et al. (2003a, 2005a) recently described several levels of effort that can be undertaken for cause
identification related to PME effects. Although the knowledge of specific causes of environmental effects
increases as one progresses through the levels of investigation, there is a concomitant increase in effort
and cost. As Dubé and MacLatchy (2001) demonstrated, it may not be necessary to progress through
the entire framework and identify causative compounds in order to mitigate effects. The Hewitt et al.
(2003a) framework includes levels to define whether there is an effect, whether it is related to the effluent
discharge facility, and whether response patterns in the receiving environment are characteristic of a
particular stressor type. The next tier of the framework involves investigating individual process wastes
within the mill to determine the components contributing to final effluent effects. Due to the complexity
encountered in trying to isolate and identify the chemicals responsible for the impacts, isolation of
process streams provides a target for more specific chemical evaluations and evaluation of stream-specific
treatment options.
In a modified version of their earlier framework, Hewitt et al. (2005a) defined pathways of investigation
of cause related to pulp and paper effects that are based on response patterns observed in biota below
pulp mills. The consistency, extent, and magnitude of response patterns in fish and benthos are first
described prior to investigating cause. The patterns themselves are then used as a first basis with which
to select different types of investigation of cause. Indeed, the information gleaned from the response
patterns themselves indicates which kinds of contaminants are present and their potential sources (e.g.,
eutrophication from inefficient nutrient management of secondary treatment). Causal investigations are
subdivided into those focused on eutrophication and those associated with a contaminant effect (including
metabolic disruption) (Hewitt et al., 2005a). In the case of nutrient enrichment, causal investigations
adopt approaches to isolate the causal nutrients and what threshold levels are involved with specific
enrichment parameters in biota. In the contaminant-focused causal investigations, questions progress
along a continuum that progresses from first asking if the source within the mill can be identified to the
compound classes involved and finally to identification of the specific chemicals associated with the
effects. In both pathways, the fundamental question driving the investigations is whether sufficient
information has been generated to define the effect such that a mitigative solution can be found.

Isolation of Causative Process Streams
The purpose of this type of source identification is to specify waste streams within the manufacturing
or treatment process that are responsible for the observed effects (Dubé and MacLatchy, 2000a,b, 2001;
Dubé et al., 2002b; Hodson et al., 1997; Martel et al., 1997; Parrott et al., 2000c). A variety of approaches
have been tried, ranging from simple, on-site static exposures involving containers of waste from different
sources within the mill (Parrott et al., 2000c) to flow-through, on-site mesocosm exposures to investigate
waste streams selected by acute toxicity tests (Dubé and MacLatchy, 2000a,b, 2001). These approaches
originated in an effort to circumvent the complexity of final effluents and to identify common sources
of bioactive substances between mills employing various production types. Munkittrick et al. (1994),