4 Plant Uptake from Wastewater Irrigation
Increasingly, wastewater, treated and untreated, has become an alternative for
diminishing freshwater reserves in water-stressed regions throughout the world
[62]. As wastewater is a known reservoir for human-use and veterinary pharmaceuticals, the reuse of wastewater represents an important pathway for these biologically
active compounds to enter the environment. As such, literature has increasingly
investigated how routine irrigation with wastewater may impact the levels of pharmaceuticals and their metabolites in plants, with a particular focus on the edible
portions included in the human diet.
4.1 Fortified Wastewater Exposure
Wastewater represents a complex matrix that is theoretically composed of a mixture
of the residues of potentially hundreds of pharmaceuticals that are consumed by the
population serviced by a particular wastewater treatment plant or WWTP [71]. This
complexity makes the study of the fate and uptake of pharmaceuticals in soil-plant
systems challenging. Therefore, studies have been undertaken using water fortified
with known concentrations of specific pharmaceuticals as a means to simplify
experiments. There have even been some efforts to develop synthetic wastewater
which provides consistent exposure of study compounds whilst increasing environmental relevance as it approaches wastewater and wastewater effluent [72, 73].
4.1.1 Impacts of Plant Species
As has been shown in soil-spiked systems, different plant species accumulate
pharmaceuticals at different rates and in various tissue compartments (e.g. root,
shoot and fruit). Studies utilising pharmaceutical-fortified irrigation water have also
demonstrated these trends. One such study fortified water to irrigate arugula (Eruca
sativa) and corn (Zea mays) with eight pharmaceutical compounds at concentrations
measured in Italian wastewater ranging from 4.6 ng/L (salbutamol) to 249 ng/L
(lincomycin) as well as mixtures 10x and 100x these measured concentrations
[74]. Lincomycin and ofloxacin were the only compounds detected above the limits
of detection in corn grain at the environmentally relevant exposures, whereas all
eight compounds were detected in the arugula leaves. Arugula uptake of three
pharmaceuticals (atenolol, sulfamethoxazole and carbamazepine) was investigated
by Kodesova et al. [29] in addition to three other vegetables (lettuce, spinach and
radish). Through their analysis of carbamazepine and its metabolism, they showed
that the two Brassicaceae species (radish and arugula) were far less efficient in
metabolising the parent compound than lettuce and spinach. Sallach et al. [75]
showed a sub-species level difference in the uptake of two antibiotic compounds
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
193
Increasingly, wastewater, treated and untreated, has become an alternative for
diminishing freshwater reserves in water-stressed regions throughout the world
[62]. As wastewater is a known reservoir for human-use and veterinary pharmaceuticals, the reuse of wastewater represents an important pathway for these biologically
active compounds to enter the environment. As such, literature has increasingly
investigated how routine irrigation with wastewater may impact the levels of pharmaceuticals and their metabolites in plants, with a particular focus on the edible
portions included in the human diet.
4.1 Fortified Wastewater Exposure
Wastewater represents a complex matrix that is theoretically composed of a mixture
of the residues of potentially hundreds of pharmaceuticals that are consumed by the
population serviced by a particular wastewater treatment plant or WWTP [71]. This
complexity makes the study of the fate and uptake of pharmaceuticals in soil-plant
systems challenging. Therefore, studies have been undertaken using water fortified
with known concentrations of specific pharmaceuticals as a means to simplify
experiments. There have even been some efforts to develop synthetic wastewater
which provides consistent exposure of study compounds whilst increasing environmental relevance as it approaches wastewater and wastewater effluent [72, 73].
4.1.1 Impacts of Plant Species
As has been shown in soil-spiked systems, different plant species accumulate
pharmaceuticals at different rates and in various tissue compartments (e.g. root,
shoot and fruit). Studies utilising pharmaceutical-fortified irrigation water have also
demonstrated these trends. One such study fortified water to irrigate arugula (Eruca
sativa) and corn (Zea mays) with eight pharmaceutical compounds at concentrations
measured in Italian wastewater ranging from 4.6 ng/L (salbutamol) to 249 ng/L
(lincomycin) as well as mixtures 10x and 100x these measured concentrations
[74]. Lincomycin and ofloxacin were the only compounds detected above the limits
of detection in corn grain at the environmentally relevant exposures, whereas all
eight compounds were detected in the arugula leaves. Arugula uptake of three
pharmaceuticals (atenolol, sulfamethoxazole and carbamazepine) was investigated
by Kodesova et al. [29] in addition to three other vegetables (lettuce, spinach and
radish). Through their analysis of carbamazepine and its metabolism, they showed
that the two Brassicaceae species (radish and arugula) were far less efficient in
metabolising the parent compound than lettuce and spinach. Sallach et al. [75]
showed a sub-species level difference in the uptake of two antibiotic compounds
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
193