(OECD 1984), McKelvie et al. [102] investigated the nuclear magnetic resonancebased metabolomic profile of E. fetida exposed for 48 days to caffeine (19.3 μg/cm
2 ),
carbamazepine (1,000 μg/cm
2 ) and estrone (1,000 μg/cm
2 ). These researchers found
that carbamazepine and estrone caused a decrease in the concentration of certain
metabolites in the whole earthworm body, although at a level of statistical significance of α ¼ 0.1. Despite the promising potential of metabolomics to elucidate the
mode of action of APIs, several questions related to tissue-specific metabolic
alterations or whether the natural environment (e.g. soil or organic matter-rich
substrates) can modulate the earthworm metabolite profile remain unanswered at
present. Genotoxic and oxidative stress have also been evaluated in E. fetida exposed
to API-spiked soils by Dong et al. [103]. DNA damage assessed by the comet assay
was the only biomarker that provided a consistent dose-dependent relationship with
tetracycline, chlortetracycline, and the combination of both antibiotics. The antioxidant enzymes catalase and superoxide dismutase had erratic responses to the
antibiotic exposure. The low number of replicates (n ¼ 3 earthworm/treatment) in
that study could be a limiting factor in concluding whether tetracycline, and chlortetracycline are oxidative stress inducers in earthworms.
Although the primary scope of ecotoxicological biomarkers is to predict adverse
effects at individual and population levels, no study reports consistent data linking
sub-individual level responses (e.g. DNA damage, antioxidant enzyme responses)
with adverse effects at higher levels of biological organisation. Therefore, the impact
of environmentally realistic concentrations of APIs on earthworms remains to be
elucidated. Moreover, the functional association between biomarker responses and
API toxicity is a challenge when the mechanism of toxic action in non-target
organisms as earthworms is unknown. The reader can find a detailed analysis of
earthworm biomarker applications in the Chap. 10 in this book.
The range of API concentrations in ecotoxicity testing normally are unrealistic,
although they could represent a worst-case scenario defined by a continue input of
APIs via biosolids application or irrigation with treated wastewater, low environmental degradation rate of APIs and soils with a high organic matter content.
Nevertheless, the effective API concentrations estimated from laboratory toxicity
testing are generally higher than those regularly detected in agricultural soils. For
example, an acute toxicity testing with 18 pharmaceuticals using E. fetida and the
standard OECD artificial soil revealed that only 8 drugs were lethal to earthworms
after 14 days of exposure. The 14d-LC 50 values were higher than API concentrations
frequently found in soil, varying between 64.8 mg/kg (ibuprofen) and 3,298 mg/kg
(propranolol) [104]. Therefore, data collected from standardised toxicity tests suggest that environmentally relevant pharmaceutical concentrations in soil, defined in
the context of background concentrations reported in the literature, do not represent a
serious risk to Eisenia species, at least at short term. However, because these epigeic
earthworms are typically used in the aerobic decomposition of solid organic waste
(particularly E. andrei [105, 106]), the question arises as: are API concentrations
measured in cattle manure or biosolids high enough as to be toxic to composting
earthworms, so compromising the vermicomposting process?
350
J. C. Sanchez-Hernandez
2 ),
carbamazepine (1,000 μg/cm
2 ) and estrone (1,000 μg/cm
2 ). These researchers found
that carbamazepine and estrone caused a decrease in the concentration of certain
metabolites in the whole earthworm body, although at a level of statistical significance of α ¼ 0.1. Despite the promising potential of metabolomics to elucidate the
mode of action of APIs, several questions related to tissue-specific metabolic
alterations or whether the natural environment (e.g. soil or organic matter-rich
substrates) can modulate the earthworm metabolite profile remain unanswered at
present. Genotoxic and oxidative stress have also been evaluated in E. fetida exposed
to API-spiked soils by Dong et al. [103]. DNA damage assessed by the comet assay
was the only biomarker that provided a consistent dose-dependent relationship with
tetracycline, chlortetracycline, and the combination of both antibiotics. The antioxidant enzymes catalase and superoxide dismutase had erratic responses to the
antibiotic exposure. The low number of replicates (n ¼ 3 earthworm/treatment) in
that study could be a limiting factor in concluding whether tetracycline, and chlortetracycline are oxidative stress inducers in earthworms.
Although the primary scope of ecotoxicological biomarkers is to predict adverse
effects at individual and population levels, no study reports consistent data linking
sub-individual level responses (e.g. DNA damage, antioxidant enzyme responses)
with adverse effects at higher levels of biological organisation. Therefore, the impact
of environmentally realistic concentrations of APIs on earthworms remains to be
elucidated. Moreover, the functional association between biomarker responses and
API toxicity is a challenge when the mechanism of toxic action in non-target
organisms as earthworms is unknown. The reader can find a detailed analysis of
earthworm biomarker applications in the Chap. 10 in this book.
The range of API concentrations in ecotoxicity testing normally are unrealistic,
although they could represent a worst-case scenario defined by a continue input of
APIs via biosolids application or irrigation with treated wastewater, low environmental degradation rate of APIs and soils with a high organic matter content.
Nevertheless, the effective API concentrations estimated from laboratory toxicity
testing are generally higher than those regularly detected in agricultural soils. For
example, an acute toxicity testing with 18 pharmaceuticals using E. fetida and the
standard OECD artificial soil revealed that only 8 drugs were lethal to earthworms
after 14 days of exposure. The 14d-LC 50 values were higher than API concentrations
frequently found in soil, varying between 64.8 mg/kg (ibuprofen) and 3,298 mg/kg
(propranolol) [104]. Therefore, data collected from standardised toxicity tests suggest that environmentally relevant pharmaceutical concentrations in soil, defined in
the context of background concentrations reported in the literature, do not represent a
serious risk to Eisenia species, at least at short term. However, because these epigeic
earthworms are typically used in the aerobic decomposition of solid organic waste
(particularly E. andrei [105, 106]), the question arises as: are API concentrations
measured in cattle manure or biosolids high enough as to be toxic to composting
earthworms, so compromising the vermicomposting process?
350
J. C. Sanchez-Hernandez