Biosolids are generally required to meet certain guidelines with respect to nutrient
and contaminant content, although pharmaceutical limits are not applicable
[98]. This may in part be related to the relatively low concentrations of pharmaceuticals in biosolids and the subsequent low risk for exposure. Whilst concentrations
are generally low, the amount of biosolids applied to land in some jurisdictions can
equate to large quantities of pharmaceuticals being transferred each year to agricultural land and being exposed to crops and soil organisms that can be essential for soil
health. It is therefore important to assess the potential exposure and risk of pharmaceuticals in these systems to ensure the ongoing beneficial reuse of biosolids can be
demonstrated to have little impact.
Comparatively few studies, however, have been undertaken to assess the potential for exposure and uptake of terrestrial organisms in agricultural systems where
biosolids have been applied. Of these studies, there have been relatively few
pharmaceuticals assessed for uptake into crops (Table 2 summarising pharmaceutical uptake in biosolid amended soils). A notable exception to this was a study by
Sabourin et al. [25] who assessed the uptake of ~50 pharmaceuticals in tomato
(Solanum lycopersicon), potatoes (Solanum tuberosum), carrots (Daucus carota)
and sweet corn (Zea mays) grown in soils amended with biosolids at a rate of 8 t/ha,
collected from nine Canadian WWTPs. Of the pharmaceuticals detected in the
biosolids only ten (atenolol, caffeine, ciprofloxacin, cocaine, epianhydrotetracycline,
glibenclamide, minocycline, naproxen, triamterene, trimethoprim) were detected in
any of the plants following biosolid addition. Furthermore, uptake into plants was
inconsistent amongst replicates, with very low (maximum 6.25 μg/kg, dry weight)
concentrations detected in respective plants, suggesting a very low potential for
uptake from recommended biosolid applications [25]. A similar trend is also apparent from a number of other studies, where relatively low uptake of pharmaceuticals
occurs through application of biosolids in uptake studies or predicted through
modelling [13, 27, 30–33, 61, 99–101]. Furthermore, the presence of biosolids
was found to reduce the uptake factors of pharmaceuticals (including carbamazepine, 17α-ethinylestradiol and salbutamol) following their addition to fortified soils,
despite their natural loads of pharmaceuticals [30, 33]. This is also consistent with
studies where biosolids were fortified with pharmaceuticals. For example, the
addition of radiolabelled carbamazepine to biosolids (equivalent to 7.6 mg/kg) and
applied to soils at 10% w/w addition rates reduced its BCF in celery (Apium
graveolens) roots, stems and leaves [61]. Specifically, the bioavailability of
14 C-carbamazepine was reduced at the end of the celery growing period which resulted in a
reduction of 38.6 Æ 18.5%, 36.5 Æ 15.9% and 63.3 Æ 6.3% of
14 C in the roots, stems
and leaves, respectively, in the 10% biosolid-amended soil. Another study used
similarly high concentrations (relative to concentrations measured in unfortified
biosolids) of carbamazepine, diphenhydramine and fluoxetine (~10 mg/kg) in spiked
biosolids to assess the uptake in soybean (Glycine max) following a relatively high
application rate (30% w/w) of biosolids to soils [13]. In this study, the total amount
of pharmaceuticals taken up was greater in the biosolid-amended soils, although the
BCF was lower for carbamazepine and diphenhydramine. These studies highlight
the ability of biosolids to decrease the bioavailability of pharmaceuticals to plants
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
201
and contaminant content, although pharmaceutical limits are not applicable
[98]. This may in part be related to the relatively low concentrations of pharmaceuticals in biosolids and the subsequent low risk for exposure. Whilst concentrations
are generally low, the amount of biosolids applied to land in some jurisdictions can
equate to large quantities of pharmaceuticals being transferred each year to agricultural land and being exposed to crops and soil organisms that can be essential for soil
health. It is therefore important to assess the potential exposure and risk of pharmaceuticals in these systems to ensure the ongoing beneficial reuse of biosolids can be
demonstrated to have little impact.
Comparatively few studies, however, have been undertaken to assess the potential for exposure and uptake of terrestrial organisms in agricultural systems where
biosolids have been applied. Of these studies, there have been relatively few
pharmaceuticals assessed for uptake into crops (Table 2 summarising pharmaceutical uptake in biosolid amended soils). A notable exception to this was a study by
Sabourin et al. [25] who assessed the uptake of ~50 pharmaceuticals in tomato
(Solanum lycopersicon), potatoes (Solanum tuberosum), carrots (Daucus carota)
and sweet corn (Zea mays) grown in soils amended with biosolids at a rate of 8 t/ha,
collected from nine Canadian WWTPs. Of the pharmaceuticals detected in the
biosolids only ten (atenolol, caffeine, ciprofloxacin, cocaine, epianhydrotetracycline,
glibenclamide, minocycline, naproxen, triamterene, trimethoprim) were detected in
any of the plants following biosolid addition. Furthermore, uptake into plants was
inconsistent amongst replicates, with very low (maximum 6.25 μg/kg, dry weight)
concentrations detected in respective plants, suggesting a very low potential for
uptake from recommended biosolid applications [25]. A similar trend is also apparent from a number of other studies, where relatively low uptake of pharmaceuticals
occurs through application of biosolids in uptake studies or predicted through
modelling [13, 27, 30–33, 61, 99–101]. Furthermore, the presence of biosolids
was found to reduce the uptake factors of pharmaceuticals (including carbamazepine, 17α-ethinylestradiol and salbutamol) following their addition to fortified soils,
despite their natural loads of pharmaceuticals [30, 33]. This is also consistent with
studies where biosolids were fortified with pharmaceuticals. For example, the
addition of radiolabelled carbamazepine to biosolids (equivalent to 7.6 mg/kg) and
applied to soils at 10% w/w addition rates reduced its BCF in celery (Apium
graveolens) roots, stems and leaves [61]. Specifically, the bioavailability of
14 C-carbamazepine was reduced at the end of the celery growing period which resulted in a
reduction of 38.6 Æ 18.5%, 36.5 Æ 15.9% and 63.3 Æ 6.3% of
14 C in the roots, stems
and leaves, respectively, in the 10% biosolid-amended soil. Another study used
similarly high concentrations (relative to concentrations measured in unfortified
biosolids) of carbamazepine, diphenhydramine and fluoxetine (~10 mg/kg) in spiked
biosolids to assess the uptake in soybean (Glycine max) following a relatively high
application rate (30% w/w) of biosolids to soils [13]. In this study, the total amount
of pharmaceuticals taken up was greater in the biosolid-amended soils, although the
BCF was lower for carbamazepine and diphenhydramine. These studies highlight
the ability of biosolids to decrease the bioavailability of pharmaceuticals to plants
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
201