Impact of study design and database parameters on NOAEL distributions used for toxicological concern (TTC) values

Plant uptake potential and soil persistence of volatile methylsiloxanes in sewage sludge amended soils

Volatile methylsiloxanes (VMSs) are organosilicon compounds, ubiquitous in modern life. Due to their high use in consumer products, large amounts of these compounds are released into sewer systems, reaching wastewater treatment plants (WWTPs). Its frequent detection in sewage sludge can be of concern when considering its land application, not only due to potential negative impacts on the environment, but also on human health. In this work, the effects of sewage sludge application on plant development and crop productivity were studied, as well as VMSs persistence in the soil and their plant uptake. This study focused on 7 VMSs (D3, D4, D5, D6, L3, L4 and L5) and consisted of a 12-week greenhouse pot experiment, where sewage sludge-amended soils were used to cultivate Pisum sativum (peas). Sewage sludge application to soils had no negative effects on plant development and was tied to crop productivity improvements. Most of the VMSs were still present in soils at the end of the experiment and plant uptake and translocation of the 4 cyclic VMSs (D3, D4, D5, D6) occurred. VMSs were detected in plant tissues up to 161 ± 27 ng g^-1 dw (samples of stems, leaves and tendrils), but did not exceed 50 ± 19 ng g^-1 dw in peas, which did not translate into a human exposure risk due to ingestion, according to an intake risk assessment. However, soil risk assessments showed that for L5 the hazardous ratios were higher than the threshold value of 1. This means a potential environmental risk despite the low levels of this compound in soils (up to 7.3 ± 0.7 ng g^-1 dw). Considering these results, sewage sludge monitoring plans should be defined for VMSs, namely when its final destination is land application, thus allowing a safer management of this residue, taking advantage of its valorization potential.

Uptake and translocation of synthetic musk fragrances by pea plant grown in sewage sludge-amended soils

Sewage sludges are rich in organic matter and several essential nutrients for plant growth, making them very appealing for application in agricultural soils. However, they may also contain a wide range of emerging pollutants, which has raised concerns about the potential risks of this practice to crops, the environment, and public health - accumulation in soils and/or plant uptake and translocation of contaminants. Therefore, there is a need to study plant-soil interactions and assess the uptake potential of these contaminants by food crops to better understand these risks. The main aim of this work was to assess the possible drawbacks of sludge application to cropland, by observing the impact on the growth and yield of a model crop (pea plant - Pisum sativum) grown over an 86-day greenhouse experiment and by assessing the uptake potential of synthetic musk fragrances. Different sewage sludge application rates (4-30-ton ha-1) and initial concentrations of contaminants were tested. The application of sludge yielded benefits to the cultivated plants, finding improved crop productivity with an application rate of 30-ton ha-1. At the end of the experiment, soil samples and plants separated into sections were analysed using a QuEChERS extraction methodology followed by gas chromatography-mass spectrometry (GC-MS) quantification. Galaxolide (HHCB) and tonalide (AHTN) underwent uptake by the plant roots, having been detected in concentrations up to 346 ng g-1 on a dry weight basis (dw), but only HHCB was detected in above ground tissues. At the end, a decrease in the levels of synthetic musks in the amended soils (>80% in several instances) was observed. Assuming the worst-case scenario, no risk to human health was observed from the ingestion of peas grown on sewage sludge-amended soils. However, a soil hazard quotient analysis yielded worryingly high quotient values for AHTN in nearly all tested conditions.

Uptake and translocation of UV-filters and synthetic musk compounds into edible parts of tomato grown in amended soils

In the last years, the number of wastewater treatment plants (WWTPs) has increased and consequently, sewage sludge production. This residue is very rich in crop nutrients, which makes it prone to be used as organic fertilizer or soil conditioner for agriculture. However, the presence of emerging pollutants in these fertilizers has raised concern, namely their potential accumulation in soil and, eventually their uptake by crops. Therefore, the main goal of this work was to study the potential plant uptake and translocation of ultraviolet-filters (UVFs) and synthetic musk compounds (SMCs). A total of 6 UVFs and 11 SMCs were analysed in Micro-Tom tomatoes grown in soil amended with a commercial sewage sludge-based organic fertilizer. Most of the studied compounds were detected in the tomato fruit, in concentrations ranging from 5 to 147 ng g^-1 dw for UVFs and from 1.3 to 68 ng g^-1 dw for SMCs. This indicates a potential uptake of these emerging pollutants and a subsequent translocation to the fruits. Besides that, UVFs show bioconcentration factors (BCFs) from 3 (DTS) to 33 (BZ) and SMCs from 0.2 (AHTN) to 23 (HHCB). Nevertheless, no risk by ingestion was observed based on estimation of the weekly exposure dose through hazard quotients (HQ < 0.02). SMCs galaxolide and tonalide seem to pose risk to the amended soils.

Analytical methodology to screen UV-filters and synthetic musk compounds in market tomatoes

A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) methodology followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis was developed to extract thirteen synthetic musk compounds (SMCs: cashmeran, celestolide, phantolide, traseolide, galaxolide, tonalide, musk ambrette, musk xylene, musk ketone, musk tibetene, musk moskene, ethylene brassylate and exaltolide) and six ultraviolet-filters (UVFs: 2-ethylhexyl 4-dimethylaminobenzoate, 3-(4'-methylbenzylidene) camphor, 2-ethylhexyl 4-methoxycinnamate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, benzophenone and drometrizole trisiloxane) from tomatoes. The proposed methodology was optimized: 2 g of freeze-dried tomato was extracted with 4 mL of water and 10 mL of ethyl acetate, adding 6 g of MgSO₄ and 1.5 g of NaCl, then a dispersive solid-phase extraction was performed using 3 g of MgSO₄, 300 mg of primary-secondary amino adsorbent (PSA) and 300 mg of octadecyl-silica (C18). Validation delivered recoveries between 81 (celestolide) and 119% (musk tibetene), with relative standard deviations <10%. The instrumental limit of detection varied from 0.02 (2-ethylhexyl 4-methoxycinnamate) to 3.00 pg (exaltolide and musk xylene). Regarding the method quantification limits, it ranged between 0.4 (celestolide) and 47.9 ng g^-1 dw (exaltolide). The method was applied to different varieties of tomatoes (Solanum lycopersicum), revealing UVFs and SMCs between 1 and 210 ng g^-1 dw. Higher concentrations were found for benzophenone (29-210 ng g^-1 dw) and galaxolide (9-53 ng g^-1 dw). The risk associated to the ingestion of contaminated tomatoes has also been estimated, showing that a potential health risk is unlikely.

Guidance on the use of the Threshold of Toxicological Concern approach in food safety assessment

The Scientific Committee confirms that the Threshold of Toxicological Concern (TTC) is a pragmatic screening and prioritisation tool for use in food safety assessment. This Guidance provides clear step-by-step instructions for use of the TTC approach. The inclusion and exclusion criteria are defined and the use of the TTC decision tree is explained. The approach can be used when the chemical structure of the substance is known, there are limited chemical-specific toxicity data and the exposure can be estimated. The TTC approach should not be used for substances for which EU food/feed legislation requires the submission of toxicity data or when sufficient data are available for a risk assessment or if the substance under consideration falls into one of the exclusion categories. For substances that have the potential to be DNA-reactive mutagens and/or carcinogens based on the weight of evidence, the relevant TTC value is 0.0025 μg/kg body weight (bw) per day. For organophosphates or carbamates, the relevant TTC value is 0.3 μg/kg bw per day. All other substances are grouped according to the Cramer classification. The TTC values for Cramer Classes I, II and III are 30 μg/kg bw per day, 9 μg/kg bw per day and 1.5 μg/kg bw per day, respectively. For substances with exposures below the TTC values, the probability that they would cause adverse health effects is low. If the estimated exposure to a substance is higher than the relevant TTC value, a non-TTC approach is required to reach a conclusion on potential adverse health effects.

Current pesticide dietary risk assessment in light of comparable animal study NOAELs after chronic and short-termed exposure durations

Dietary risk assessment (DRA) of pesticides includes the estimation of chronic and acute exposures from crop residues, but assesses acute exposures only for pesticides with an acute reference dose (ARfD). Acute estimation uses high percentiles of food consumption surveys which are considerably higher than per capita lifetime averaged food consumption values which are used for chronic estimations. Assessing acute risks only for pesticides with an ARfD tacitly assumes that chronic risk assessment covers also intermittent occurring exposures which could significantly exceed chronic estimates. The present investigation conducted on 2200 rat studies from 436 pesticides provides evidence demonstrating that pesticides with and without ARfD have no-observed-adverse-effect levels (NOAELs) which remain statistically unchanged in developmental, subacute, subchronic, reproductive and chronic toxicity studies covering exposure durations between 2 and 104 weeks. DRA of pesticides without ARfD needs reconsideration in light of equally high toxic dose levels after short- and long-term exposures, suggesting that intermittent exposures could be toxic, if they repeatedly exceed the acceptable chronic daily intake (ADI; conceptually the human counterpart of chronic animal NOAEL). As such risks are currently not assessed for pesticides without ARfD, the current DRA concept, which automatically presumes the use of low chronic exposure estimates entirely covers the risks of not acutely toxic pesticides, needs reconsideration. Furthermore, risks to intermittent occurring high exposures are probably also insufficiently assessed for pesticides where the ARfD is significantly higher than the ADI. As an example, the maximum residue limit for bifenazate in peaches is discussed.