When rohu fish are exposed to a low but toxic level of a blue dye used in fish farms, their blood loses a lot of its oxygen-carrying capacity, making them very weak.
Scientific Claim
Exposure to sub-lethal methylene blue (1/5th of 96-hour LC50 = 1.7 mg/L) for 28 days is associated with a 51% reduction in hemoglobin levels (from 9.8 ± 0.3% to 4.8 ± 0.3%) in Labeo rohita fish, indicating a strong link between methylene blue exposure and anemia in this species.
Original Statement
“Hb% declined by 51% (4.8 ± 0.3%) in the 1/5th LC50 group by day 28”
Evidence Quality Assessment
Claim Status
overstated
Study Design Support
Design cannot support claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The abstract uses language implying causation ('MB-induced anemia'), but the study design is observational and lacks randomization or control group details. Only association can be claimed.
More Accurate Statement
“Exposure to sub-lethal methylene blue (1/5th of 96-hour LC50 = 1.7 mg/L) for 28 days is associated with a 51% reduction in hemoglobin levels (from 9.8 ± 0.3% to 4.8 ± 0.3%) in Labeo rohita fish, indicating a link between methylene blue exposure and reduced oxygen-carrying capacity in this species.”
Evidence from Studies
Supporting (1)
The study found that when fish were exposed to a low but prolonged dose of methylene blue, their blood lost over half its hemoglobin — the molecule that carries oxygen — which means they developed anemia, exactly as the claim says.