2009 – January 14^th.  Effluent containing neuroactive substances from some pulp and paper mills is linked with damage to fish in nearby waters.

A new pulp fact?

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

ES&T Environmental News

Environ. Sci. Technol.

DOI: 10.1021/es803564j

January 14, 2009

Robert Weinhold

Effluent containing neuroactive substances from some pulp and paper mills is linked with damage to fish in nearby waters.

ESTORMIZ, COURTESY OF WIKIMEDIA COMMONS

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 "pulp and Paper Mill Effluents Contain Neuroactive

Substances That Potentially Disrupt Neuroendocrine Control of Fish

Reproduction" http://pubs.acs.org/doi/abs/10.1021/es802552m  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

http://www.compphys.uottawa.ca/index.php?/Trudeau/Index/ 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, ?-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

http://www.ncbi.nlm.nih.gov/pubmed/18657592 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 http://emt.oregonstate.edu/faculty/curtis.htm

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

http://www.physiology.gu.se/endo/staff/JL.htm 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.

http://www.agriculture.purdue.edu/fnr/faculty/sepulveda/index.htm "[These

findings] will inspire a lot of folks, especially in developing countries

that have lots of issues with paper mill plants."