[Pharmwaste] effluent from pulp mills affecting fish populations article

[Tenace, Laurie]

A little off topic - Laurie

http://pubs.acs.org/doi/full/10.1021/es803564j


A new pulp fact?
Environ. Sci. Technol., 
January 14, 2009

If you’re reading this on paper, you may want to thank fish populations
around the world for their sacrifices. Despite the paper industry’s efforts
to reduce contamination, numerous studies have shown that effluent from pulp
and paper mills discharged to nearby waters is linked with plummeting fish
populations, alterations in sex-hormone levels and physical characteristics
of sex organs, and other changes such as reduced egg production.

However, the specific mechanisms through which such damage occurs remain
unclear. In a study published in ES&T (DOI 10.1021/es802552m), a team of
researchers from Canada and the U.S. says it has identified several rarely
explored pathways that may be plausible candidates.

Instead of studying direct endocrine disruption through research on endocrine
organs, as many have done, the team evaluated several neurochemical pathways,
which have essential regulatory roles in fish reproduction, says Vance
Trudeau of the University of Ottawa and the study’s coauthor. These pathways
include receptors, which can change the function of the cells to which they
are attached, and enzymes, which act as catalysts for various cellular and
body functions. The four receptors and four enzymes that the researchers
selected had been identified in other studiesa dozen of which they cite in
their paperas important reproductive neurotransmission components.

The receptors included dopamine-2, γ-aminobutyric acid (GABA),
N-methyl-d-aspartic acid, and muscarinic acetylcholine (mACh). The enzymes
included monoamine oxidase, GABA-transaminase, acetylcholinesterase, and
glutamic acid decarboxylase (GAD).The researchers obtained samples of
primary- and secondary-treated effluent from an unnamed newsprint mill in
eastern Canada. The stored samples, taken on various dates, were processed
from February 1 to May 1, 2007. They used five media, including ethyl
acetate, water, and ethanol, to extract various compounds from the effluent
samples.

Back in the lab, the scientists exposed brain tissue from common goldfish to
one standard concentration of each extract sample of 0.5 milligrams per
milliliter. They used a fixed concentration to make direct comparisons
between all the extracts, which had highly variable yields of many
substances. Some researchers have concluded that goldfish are good model
organisms for evaluating neuroendocrine signaling and for regulating
reproduction in a number of vertebrates.

The team evaluated 80 possible combinations of receptors, enzymes, extraction
media, and effluent types. For instance, one combination looked at exposure
of the receptor dopamine-2 to substances extracted from primary-treated
effluent using ethyl acetate. Another combination looked at exposure of the
enzyme acetylcholinesterase to substances extracted from secondary-treated
effluent using hexane. Of the 80 possible combinations, 32 showed a
significant difference compared with controls, increasing or decreasing
receptor binding or enzyme activity by anywhere from −75.1% to 188.9%.Both
types of effluent and all extraction media were linked with significant
impacts to the brain tissues, indicating that a wide range of substances in
the effluents was impacting the neurochemical pathways. The researchers
report that each of the five media used for extraction affected activity in
5−7 of the 16 possible scenarios. Only GAD wasn’t significantly affected by
any extraction product. The mACh receptor was significantly affected by one
extraction product only. The other six receptors and enzymes were
significantly affected by 3−6 extraction products, out of 10 possible.
Extracts from the primary and secondary effluent had different effects, but
each affected roughly the same number of possible combinations (18 of 40 for
primary, 14 of 40 for secondary).“These findings provide a novel and
plausible mechanism by which pulp and paper mill effluents impair fish
reproduction by interacting with neurotransmitter systems,” the team writes
in its study. Oregon State University’s Lawrence Curtis agrees: “[The paper]
identifies potential new modes of action of pulp and paper mill effluent
toxicity.”

However, as Curtis, the authors, and others note, the study has many
limitations. The variables that still need to be tested include different
types of wood; a range of pulping and papermaking processes around the world;
seasonal changes in effluent content; different responses by various fish
species; and variations in waterway traits such as biology, chemistry, and
flow.

In addition, the team’s use of a single exposure concentration doesn’t offer
insight on whether the receptor and enzyme responses were affected by either
receptor destruction or displacement caused by competitive binding of
different chemicals to the receptors, says Joakim Larsson of Sweden’s
Goteborg University. “Normally one would require testing of a range of
concentrations,” he says. “In [this] study, it is not clear what kind of
receptor interactions we are talking about, and thus it is more difficult to
judge the meaning of the data.”Larsson also cautions that the in vitro
methods used in the study don’t reflect realistic environmental exposures:
“It is not clear if any of the unknown components of the effluents showing
some effect in the in vitro assays actually can get into a real, live fish.
And even if these components are taken up, do they reach a sufficiently high
concentration in the fish to directly impair neuroendocrine signaling in
vivo? Showing this would be a major step forward.”Despite these limitations,
“this type of biomarker will be really useful,” says Maria Sepulveda of
Purdue University. “[These findings] will inspire a lot of folks, especially
in developing countries that have lots of issues with paper mill plants.”

Laurie Tenace
Environmental Specialist
Waste Reduction Section
Florida Department of Environmental Protection
2600 Blair Stone Rd., MS 4555
Tallahassee FL 32399-2400
P: 850.245.8759
F: 850.245.8811

Mercury: http://www.dep.state.fl.us/waste/categories/mercury/default.htm 

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