[51]. This is in line with the study by Pino et al. [54], which calculated an EC 50 value
for the parameter of root elongation inhibition in this same plant species of 2,820 mg/
L. Similar trends were observed by An et al. [55] after exposing the plant Triticum
aestivum L (wheat) to paracetamol. In this case, the obtained acute EC 50 value for the
parameter of root elongation inhibition was of 668.8 mg/L, which is well above
environmental levels. However, prolonged exposures to this substance yielded
distinct profiles of toxic effects, evidencing the pro-oxidative nature of paracetamol.
Periods of 7 and 14 days of exposure were enough to alter the antioxidant status of
exposed plants, and following a 21-day period of exposure, growth was
compromised, as well as chlorophyll levels and protein biosynthesis. In a study
conducted with Lemna minor by Kummerová et al. [56], it was possible to observe
that parameters such as plant number, biomass production, and leaf area size were
only slightly changed by paracetamol, in contrast with biochemical and histological
traits that were severely affected by this drug. Among the most impacted biomarkers,
one could find a significant decrease in levels of photosynthetic pigments, and an
increase in non-photochemical quenching; consequently, the relative chlorophyll
fluorescence was strongly compromised. These effects were associated to increased
levels of reactive oxygen and nitrogen species and to the activation of antioxidant
defensive mechanisms. The study conducted by Nunes et al. [57] showed that the
comparative sensitivity toward paracetamol may vary considerably, even when
studying phylogenetically close plant species, such as Lemna minor and Lemna
gibba. The obtained results clearly indicated that L. minor was more sensitive than
L. gibba in terms of the pro-oxidative effects, since this species was capable of
activating an antioxidant response involving the amino acid proline, which is known
for its antioxidant properties.
1.4 Toxic Effects of Paracetamol on Polychaetes
and Mollusks
Despite the general absence of studies focusing on this specific issue, invertebrates
such as polychaete and mollusk species seem also to respond to paracetamol
exposure, with the activation of metabolic and antioxidant mechanisms. This was
the case identified by Brandão et al. [58], when studying the responses elicited by
this chemical on the freshwater bivalve Corbicula fluminea. The obtained results
evidenced an antioxidant response triggered by paracetamol, following both shortand long-term exposures, with the involvement of two of the tested biomarkers,
namely, glutathione-S-transferases and glutathione reductase activities, which were
significantly depressed. The study by Antunes et al. [59] was also demonstrative that
bivalves, despite being from distinct species and habitats, could also respond to the
presence of paracetamol. In fact, the pattern of responses deployed by two species of
estuarine/marine clams, namely, Ruditapes decussata and Ruditapes philippinarum,
were somewhat similar to the one described for C. fluminea. Changes in GST
136
B. Nunes
for the parameter of root elongation inhibition in this same plant species of 2,820 mg/
L. Similar trends were observed by An et al. [55] after exposing the plant Triticum
aestivum L (wheat) to paracetamol. In this case, the obtained acute EC 50 value for the
parameter of root elongation inhibition was of 668.8 mg/L, which is well above
environmental levels. However, prolonged exposures to this substance yielded
distinct profiles of toxic effects, evidencing the pro-oxidative nature of paracetamol.
Periods of 7 and 14 days of exposure were enough to alter the antioxidant status of
exposed plants, and following a 21-day period of exposure, growth was
compromised, as well as chlorophyll levels and protein biosynthesis. In a study
conducted with Lemna minor by Kummerová et al. [56], it was possible to observe
that parameters such as plant number, biomass production, and leaf area size were
only slightly changed by paracetamol, in contrast with biochemical and histological
traits that were severely affected by this drug. Among the most impacted biomarkers,
one could find a significant decrease in levels of photosynthetic pigments, and an
increase in non-photochemical quenching; consequently, the relative chlorophyll
fluorescence was strongly compromised. These effects were associated to increased
levels of reactive oxygen and nitrogen species and to the activation of antioxidant
defensive mechanisms. The study conducted by Nunes et al. [57] showed that the
comparative sensitivity toward paracetamol may vary considerably, even when
studying phylogenetically close plant species, such as Lemna minor and Lemna
gibba. The obtained results clearly indicated that L. minor was more sensitive than
L. gibba in terms of the pro-oxidative effects, since this species was capable of
activating an antioxidant response involving the amino acid proline, which is known
for its antioxidant properties.
1.4 Toxic Effects of Paracetamol on Polychaetes
and Mollusks
Despite the general absence of studies focusing on this specific issue, invertebrates
such as polychaete and mollusk species seem also to respond to paracetamol
exposure, with the activation of metabolic and antioxidant mechanisms. This was
the case identified by Brandão et al. [58], when studying the responses elicited by
this chemical on the freshwater bivalve Corbicula fluminea. The obtained results
evidenced an antioxidant response triggered by paracetamol, following both shortand long-term exposures, with the involvement of two of the tested biomarkers,
namely, glutathione-S-transferases and glutathione reductase activities, which were
significantly depressed. The study by Antunes et al. [59] was also demonstrative that
bivalves, despite being from distinct species and habitats, could also respond to the
presence of paracetamol. In fact, the pattern of responses deployed by two species of
estuarine/marine clams, namely, Ruditapes decussata and Ruditapes philippinarum,
were somewhat similar to the one described for C. fluminea. Changes in GST
136
B. Nunes