control treatments. In addition, ibuprofen treatment resulted in statistically significant enhancement of lettuce primary root development in comparison to control.
These results support earlier findings that impacts upon higher plants not only are
compound specific but also differ between plant species.
It is important to highlight that the majority of studies which have elucidated the
effect of antibiotics on plants have used much higher exposure concentrations into a
growth medium, which do not resemble in vivo situations occurring in the natural
soil environment (e.g. Liu et al. [126] (100–500,000 μg/ L), Michelini et al. [127]
(11,500 μg/L), Migliore et al. [128] (5–50,000 μg L), Michelini et al. [129]
(10000–200,000 μg/kg)). More recently, research has started to explore the potential
for sublethal effects, or changes in key plant parameters at lower, environmentally
relevant concentrations [130, 131].
7.2 Soil Invertebrate Toxicity
There is a general paucity of published scientific literature concerning the ecotoxicity
of pharmaceuticals in soil invertebrates, with a majority of the data that is available
focussed on earthworm species. Research has primarily centred on evaluating the
effects of veterinary pharmaceuticals (antibiotics) with the most common end points
considering survival, reproduction and alterations in behaviour such as avoidance
and surfacing in response to pharmaceutical exposure. As with uptake in terrestrial
invertebrates, studies have also tended to focus on earthworm species. Research
published by Litskas et al. [132] revealed amoxicillin had no significant effects on
reproduction or weight gain of earthworms (E. fetida) across the concentration range
of 0.64–78.89 mg/kg soil. The effects of another antibiotic, doxycycline, on earthworm reproduction were later published by Litskas et al. [133]. Whilst no effects on
earthworm weight were observed following 28 days of exposure to doxycycline,
negative effects on the total number of juvenile earthworms were observed at the
concentration level of 30 mg/kg soil. Comparatively, doxycycline did not induce
effects on earthworm reproduction or mortality following the application of doxycycline spiked pig slurry (75 and 7,500 μg/mL) to a series of soil columns
[134]. Low toxicity of antibiotics (sulphamethoxazole, trimethoprim and tetracycline) was also observed by Pino et al. [135] as none of the selected antibiotics were
toxic to E. fetida below 2000 mg/kg. Similarly no mortality of earthworms (E .fetida)
was observed in a multispecies-soil system at the highest oxytetracycline concentration used (100 mg/kg) [136] However, other tetracycline antibiotics have been
shown to significantly impact on earthworms. For example, Lin et al. [137] showed
that the total number of juveniles was reduced after exposure to chlortetracycline,
with effect concentrations (EC 50 values) for juveniles reported at 96.1 mg/kg. Chlortetracycline also reduced cocoon counts (EC 50 120.3 mg/kg) and induced physiological responses and genotoxicity in earthworms.
The effects of antibiotics on earthworms reported by Pino et al. [135] were part of
a wider study which evaluated the ecotoxicity of 18 pharmaceuticals which included
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
207
These results support earlier findings that impacts upon higher plants not only are
compound specific but also differ between plant species.
It is important to highlight that the majority of studies which have elucidated the
effect of antibiotics on plants have used much higher exposure concentrations into a
growth medium, which do not resemble in vivo situations occurring in the natural
soil environment (e.g. Liu et al. [126] (100–500,000 μg/ L), Michelini et al. [127]
(11,500 μg/L), Migliore et al. [128] (5–50,000 μg L), Michelini et al. [129]
(10000–200,000 μg/kg)). More recently, research has started to explore the potential
for sublethal effects, or changes in key plant parameters at lower, environmentally
relevant concentrations [130, 131].
7.2 Soil Invertebrate Toxicity
There is a general paucity of published scientific literature concerning the ecotoxicity
of pharmaceuticals in soil invertebrates, with a majority of the data that is available
focussed on earthworm species. Research has primarily centred on evaluating the
effects of veterinary pharmaceuticals (antibiotics) with the most common end points
considering survival, reproduction and alterations in behaviour such as avoidance
and surfacing in response to pharmaceutical exposure. As with uptake in terrestrial
invertebrates, studies have also tended to focus on earthworm species. Research
published by Litskas et al. [132] revealed amoxicillin had no significant effects on
reproduction or weight gain of earthworms (E. fetida) across the concentration range
of 0.64–78.89 mg/kg soil. The effects of another antibiotic, doxycycline, on earthworm reproduction were later published by Litskas et al. [133]. Whilst no effects on
earthworm weight were observed following 28 days of exposure to doxycycline,
negative effects on the total number of juvenile earthworms were observed at the
concentration level of 30 mg/kg soil. Comparatively, doxycycline did not induce
effects on earthworm reproduction or mortality following the application of doxycycline spiked pig slurry (75 and 7,500 μg/mL) to a series of soil columns
[134]. Low toxicity of antibiotics (sulphamethoxazole, trimethoprim and tetracycline) was also observed by Pino et al. [135] as none of the selected antibiotics were
toxic to E. fetida below 2000 mg/kg. Similarly no mortality of earthworms (E .fetida)
was observed in a multispecies-soil system at the highest oxytetracycline concentration used (100 mg/kg) [136] However, other tetracycline antibiotics have been
shown to significantly impact on earthworms. For example, Lin et al. [137] showed
that the total number of juveniles was reduced after exposure to chlortetracycline,
with effect concentrations (EC 50 values) for juveniles reported at 96.1 mg/kg. Chlortetracycline also reduced cocoon counts (EC 50 120.3 mg/kg) and induced physiological responses and genotoxicity in earthworms.
The effects of antibiotics on earthworms reported by Pino et al. [135] were part of
a wider study which evaluated the ecotoxicity of 18 pharmaceuticals which included
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
207