being usually effectively eliminated at sewage treatment plants (STPs; [32]; Falås
et al. [33]; [29, 34]), paracetamol is persistent in the aquatic environment [35], being
consequently found in receiving waters. Even advanced techniques and procedures
of wastewater treatment are not completely efficient in removing paracetamol from
such matrices [36], and paracetamol ends up being released into receiving waters,
where it may attain considerable levels. Paracetamol is also prone to be degraded by
bacterial metabolism, as reviewed by Żur et al. [37]. Bacteria from the genera
Pseudomonas, Bacillus, Acinetobacter, and Sphingomonas are particularly effective
in degrading this drug [38], which might in the future decisively contribute for an
increased efficacy of wastewater treatment solutions for this specific drug. Nevertheless, the efficacy of such degradation processes, in the wild, is not effective
enough to prevent paracetamol from being somewhat abundant in aquatic ecosystems. In fact, the generalized environmental presence and high levels of paracetamol
have been considered particularly troublesome in some locations. The work by
Ashfaq et al. [39] established that paracetamol presented the higher environmental
risk among a series of pharmaceutical drugs (paracetamol, naproxen, diclofenac,
ibuprofen, amlodipine, rosuvastatin, ofloxacin, ciprofloxacin, moxifloxacin,
sparfloxacin, and gemifloxacin), which resulted from the released of contaminated
effluents from Pakistan pharmaceutical industry units. Specific locations, where the
network of sewage treatment facilities does not exist or is not entirely functional,
have levels of paracetamol well above those reported to occur in countries where
most sewage is effectively treated. This is the case of several African countries [40],
evidencing that human excreta are the major sources of paracetamol in the wild.
Values of paracetamol levels determined in Kenya reach 106,970 ng/L, as determined by K’oreje et al. [41], but this corresponds to an extreme value that may be
interpreted as a worst-case scenario of contamination. Despite being considerably
lower, paracetamol is ubiquitous in aquatic ecosystems. The presence of paracetamol
in freshwater systems has been already documented, in levels up to 653.5 pg/L (Dal
River, Sweden; [35]), 1,289 ng/L (Lobregat River, Spain; [42]), 10 μg/L (freshwater
streams, USA; [43]), above 65 μg/L (Tyne River, UK; [44]), 30.421 ng/L
(Monjolinho River, Brazil; [45]), and 610 ng/L (Savar River, Serbia; [46]). Paracetamol presence was also reported in marine waters (76.9 ng/L, determined at Vila do
Conde, Portugal; [47]) and even drinking water (211 ng/L, water sample collected in
France; [48]).
1.2 Ecotoxicological Effects Caused by Paracetamol
Considering the already found levels of paracetamol in the wild, its persistence, and
the described patterns of metabolism and toxic effects, it is not surprising that
paracetamol may exert deleterious alterations in exposed biota. In fact, a considerable number of studies has focused on characterizing adverse effects caused by
paracetamol on multiple species, and the common conclusion is that it may exert
significant toxicity in most organisms, namely, with the involvement of oxidative
134
B. Nunes
et al. [33]; [29, 34]), paracetamol is persistent in the aquatic environment [35], being
consequently found in receiving waters. Even advanced techniques and procedures
of wastewater treatment are not completely efficient in removing paracetamol from
such matrices [36], and paracetamol ends up being released into receiving waters,
where it may attain considerable levels. Paracetamol is also prone to be degraded by
bacterial metabolism, as reviewed by Żur et al. [37]. Bacteria from the genera
Pseudomonas, Bacillus, Acinetobacter, and Sphingomonas are particularly effective
in degrading this drug [38], which might in the future decisively contribute for an
increased efficacy of wastewater treatment solutions for this specific drug. Nevertheless, the efficacy of such degradation processes, in the wild, is not effective
enough to prevent paracetamol from being somewhat abundant in aquatic ecosystems. In fact, the generalized environmental presence and high levels of paracetamol
have been considered particularly troublesome in some locations. The work by
Ashfaq et al. [39] established that paracetamol presented the higher environmental
risk among a series of pharmaceutical drugs (paracetamol, naproxen, diclofenac,
ibuprofen, amlodipine, rosuvastatin, ofloxacin, ciprofloxacin, moxifloxacin,
sparfloxacin, and gemifloxacin), which resulted from the released of contaminated
effluents from Pakistan pharmaceutical industry units. Specific locations, where the
network of sewage treatment facilities does not exist or is not entirely functional,
have levels of paracetamol well above those reported to occur in countries where
most sewage is effectively treated. This is the case of several African countries [40],
evidencing that human excreta are the major sources of paracetamol in the wild.
Values of paracetamol levels determined in Kenya reach 106,970 ng/L, as determined by K’oreje et al. [41], but this corresponds to an extreme value that may be
interpreted as a worst-case scenario of contamination. Despite being considerably
lower, paracetamol is ubiquitous in aquatic ecosystems. The presence of paracetamol
in freshwater systems has been already documented, in levels up to 653.5 pg/L (Dal
River, Sweden; [35]), 1,289 ng/L (Lobregat River, Spain; [42]), 10 μg/L (freshwater
streams, USA; [43]), above 65 μg/L (Tyne River, UK; [44]), 30.421 ng/L
(Monjolinho River, Brazil; [45]), and 610 ng/L (Savar River, Serbia; [46]). Paracetamol presence was also reported in marine waters (76.9 ng/L, determined at Vila do
Conde, Portugal; [47]) and even drinking water (211 ng/L, water sample collected in
France; [48]).
1.2 Ecotoxicological Effects Caused by Paracetamol
Considering the already found levels of paracetamol in the wild, its persistence, and
the described patterns of metabolism and toxic effects, it is not surprising that
paracetamol may exert deleterious alterations in exposed biota. In fact, a considerable number of studies has focused on characterizing adverse effects caused by
paracetamol on multiple species, and the common conclusion is that it may exert
significant toxicity in most organisms, namely, with the involvement of oxidative
134
B. Nunes