Are environmental concentrations of methotrexate and
tamoxifen toxic for the aquatic biota?
G.V. Aguirre-Martínez, 1, 2* C. Okello, 1, 3 M.J. Salamanca, 1, T.A. Del Valls, 1 C.
Garrido, 2 M.L. Martín-Díaz, 1, 2
1) Cátedra UNESCO/UNITWIN/WiCop. Facultad Ciencias del Mar y Ambientales.
Universidad de Cádiz, Polígono Río San Pedro s/n. P. Real, Cádiz, Spain. 2)
Andalusian Center of Marine Science and Technology (CACYTMAR). Campus
Universitario de Puerto Real. 11510, Puerto Real. Cádiz. Spain. 3) Integrated
Geoscience Research Group (IGRG), Interdepartmental Centre for Environmental
Sciences Research (CIRSA). Ravenna Campus. University of Bologna. Via S. Alberto
163. 48100 Ravenna, Italy.
*Presenting author contact: gabriela.aguirre@uca.es
Despite detected concentrations in the environment, most methotrexate (MTX) and
tamoxifen (TMX) research is essentially bio-medically orientated with few studies
addressing the question of toxicity in aquatic organisms. MTX is a commonly used antimetabolite (folic acid antagonist) in cancer treatment and applied as anti-rheumatic
drug, while TMX is commonly used for breast cancer treatment. Both compounds have
been determined in the aquatic environment. In the preset study, these compounds
were examined in the laboratory with regard on acute and chronic toxicity towards five
species Vibrio fisheri (Proteobacteria), Selenastrum capricornotum (Clorophyta),
Isochrysis galbana (Haptophyta), Paracentrotus lividus (Echinodermata) and Ruditapes
philippinarum (Mollusca), in order to assess potential sublethal responses after short
and long-term exposure to MTX and TMX including bioluminescence response in
bacteria, growth inhibition in microalgae, fertilization success and larval development in
sea urchin, lysosomal membrane stability (LMS) and several biomarkers in clams
tissues. TMX was observed to be more toxic to V. fisheri than MTX, however at
concentrations that are not likely to occur in the environment. Regarding growth
inhibition in microalgae, it was showed that TMX at 50, 100, 500 mg·L-1 was
significantly more toxic than MTX (p < 0.01). I. galbana was significantly more sensitive
to both pharmaceuticals than S. capricornutum. Similarly TMX and MTX at 50, 100,
500 mg L-1 provoked an adverse effect on fertilization success of P. lividus being TMX
significantly more toxic than MTX (p < 0.01). Teratogenic effect was observed in P.
lividus when exposed to MTX at 50 μg L-1 and TMX at 0.001 μg·L-1 (p < 0.01).
Environmental concentrations of TMX induced significantly LMS alteration and
sublethal adverse effects in clams compared to controls after 21 days of exposure (p <
0.05). Acute and chronic effects studied in this research indicated that MTX was not
toxic for these species at environmental relevant concentrations, while TMX resulted to
be potentially toxic for aquatic biota.
Key words: clams, sea urchin, microalgae, bioassay, vibrio fishery, acute toxicity.