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The experiment involved Daphnia, a tiny shrimp-like freshwater animal which has been extensively studied and is used as an eco-indicator for environmental problems because of its importance in many food webs.
Daphnia were fed on glyphosate-tolerant GM ('Roundup Ready') soya grown on eight different farm fields in Iowa.
Since the species used has a life-span of only a few weeks, scientists were able to examine the effect of its diet on an array of key events in its life-cycle.
Aware that most previous studies have neglected to check actual residues of glyphosate herbicide or AMPA (its major derivative) in the test feed, the scientists measured both.
As expected, all the Roundup Ready soya feeds contained glyphosate residues, and all were below the maximum permitted level. However, there was a 15-fold difference between the highest and lowest residues detected. This amount of unassessed variability in the test materials casts doubt on the validity of previous 'safety' studies using commercial Roundup Ready soya.
In all but one sample there was more AMPA than glyphosate. Since both glyphosate and AMPA are toxic, tests based on glyphosate alone may disguise a problem present in real-world exposure.
Although the statistical associations were not strong, glyphosate residues showed a consistent and significant negative effect on a range of life-history traits, including growth, time to reproductive maturity and number of offspring. Previous studies have demonstrated reduced survival, growth and reproduction attributable to Roundup and glyphosate contamination in the environment of Daphnia.
Aquatic animals are now likely to be exposed to Roundup in both their food and surroundings. It seems the herbicide formula won't kill them outright but certainly reduces their survival fitness, and could progressively erode an important link in the natural ecosystem with ramifications on an environmental scale.
The shortened survival of the Daphnia fed GM soya didn't show a consistent dose-dependence on glyphosate residue level. This again raises the perennial question of the presence of other, more harmful, ingredients in the various formulations of 'Roundup' now in commercial use.
Since GM soya is used increasingly in fish farms, this study has implications for the wholesomeness of the produce generated in them.
This study deals a sorry blow to the notion that GM soya is substantially equivalent to conventional soya, and to Roundup's reputation as an environmentally safe herbicide which doesn't harm animals.
It shows clearly that too short or too long an exposure time chosen as the period of study could fail to reveal reduced survival, growth-impairment and fertility limitations. The routine 90-day rodent feeding study is entirely inadequate to pickup any of these problems. Likewise using livestock, which rarely survive much beyond adolescence, as evidence of GM food safety is absurd.
As the authors point out, while Daphnia has many physiological responses unique to such animals, much valuable information with relevance to mammals can be gained using animals with a short life-span and generation time.
Studying in a few weeks what would take hundreds of years to do in humans clearly has a value. We just need to do it.
- Marek Cuhra, et al., 2015, Glyphosate-Residues in Roundup-Ready Soybena Impair Daphnia magna Life-Cycle, Journal of Agricultural Chemistry and Environment