Exploring the destiny and distribution of thiocyanate in the water-soil-plant system and the potential impacts on human health.

Endocrine disruptors like thiocyanate are some of the principal causes of chronic disorders worldwide. Prenatal and postnatal exposure to thiocyanate can interfere with normal neurological development in both fetuses and newborns. Currently, little information regarding thiocyanate levels and potential sources of exposure is available. In this study, we evaluated thiocyanate uptake and accumulation in chard and spinach grown under greenhouse conditions. Both chard and spinach are commonly used to produce baby foods. Three thiocyanate concentrations were compared: Control, T1 (30 ng mL-1), and T2 (70 ng mL-1). Thiocyanate accumulation depended on the concentration and exposure time. Chard was found to accumulate more thiocyanate than spinach, with leaf accumulation > stem accumulation (p < 0.0194) and maximum concentrations of 76 ng g-1 (control), 112 ng g-1, (T1), and 134 ng g-1 (T2). The estimated daily intake (EDI) of thiocyanate for chard and spinach (fresh) exceeded the subchronic reference dose of 200 ng-1 kg-1 day-1 and the chronic reference dose of 600 ng-1 kg-1 day-1. In addition, the EDI of thiocyanate for spinach in baby food exceeded twice the chronic reference dose in the vulnerable newborn-1 year age group. However, all EDIs were lower than the lowest observed adverse effect level (LOAEL) of 1.9 × 105 ng kg-1 day-1. Further studies are needed that increase our knowledge of thiocyanate levels and potential environmental sources to reduce opportunities for exposure, especially in vulnerable groups.

Occurrence, distribution and dynamics of perchlorate in soil, water, fertilizers, vegetables and fruits and associated human exposure in Chile.

Perchlorate (ClO4-) has been identified as a persistent environmental contaminant of concern. Perchlorate exposure is a potential health concern because it interferes with hormone production by thyroid gland. Food (fruits and vegetables) and drinking water are an important source of human exposure to perchlorate. However, little is known about the occurrence of perchlorate in Chile. The purpose of this study was to determine the occurrence of perchlorate in 145 samples (soil, drinking water, surface water, groundwater, fertilizers, fruits and vegetables) collected across Chile and estimate associated exposure to consumers. Our results show that perchlorate was detected in soil (median: 22.2 ng g-1), drinking water (median: 3.0 ng mL-1), fruits (median: 0.91 ng g-1 fresh weight [FW]), lettuce (median: 5.0 ng g-1 FW) and chard (median: 4.15 ng g-1 FW). Interestingly, perchlorate concentrations detected in drinking water from three regions (Serena, Copiapo and Illapel) exceeded the USEPA interim drinking water health advisory level of 15 ng mL-1. Median concentrations of perchlorate in non-nitrogenous fertilizers (3.1 mg kg-1) were higher than those in nitrogenous fertilizers (1.3 mg kg-1). Estimated daily intake (EDI) of perchlorate via drinking water was lower than the USEPA's reference dose (7000 ng kg-1 bw day-1). The EDI of perchlorate via vegetables (chard and lettuce) produced in northern Chile was three times higher than those produced in other regions. The results of this study provide information about perchlorate sources in Chile, which will be helpful in modifying current regulations.

Accumulation and distribution of perchlorate in spinach and chard growing under greenhouse: Implications for food safety in baby foods commodities.

Very little information is available with regards to the bioavailability of perchlorate in spinach or chard used in the production of baby foods commodities. In the present study, the uptake and accumulation of perchlorate were compared under two different treatments (T1: 1 and T2: 10 mg L-1 ClO4-). Our results indicate that spinach has a higher capacity to accumulate perchlorate than chard (p < 0.0185). Concentrations of perchlorate in leaves, stems and roots (leaves > stem > roots) all gradually increased (p < 0.0001) as vegetable growing and treatment (T2 > T1). No significant differences were found between the control and T1. The daily intake for perchlorate (control) is below the proposed international standard, however, it was exceeded in T1 and T2. The results suggested that perchlorate is actively accumulate in high concentrations in vegetables used in the production of baby food commodities and the exposure of perchlorate via the food consumption (baby foods) was evaluated as not safe.

Sources and fates of perchlorate in soils in Chile: A case study of perchlorate dynamics in soil-crop systems using lettuce (Lactuca sativa) fields.

Perchlorate occurs naturally in the environment in deposits of nitrate and can be formed in the atmosphere and precipitate into soil. However, little is known about the occurrence and levels of perchlorate in soils and fertilizers in Chile and its impacts on agricultural systems and food safety. In this study, concentrations of perchlorate were determined in 101 surface soils and 17 fertilizers [nitrogenous (n = 8), nitrogen-phosphorous-potassium (NPK; n = 3), phosphate (n = 2) and non-nitrogenous (n = 4)] collected across Chile from 2017 to 2018. Our results show that perchlorate was detected mainly in agricultural soils (mean: 0.32 ng g-1), grassland rotation sites (0.41 ngg-1) and urban locations (0.38 ng g-1). Interestingly, elevated concentrations of perchlorate (9.66 and 54.0 ng g-1) were found in agricultural soils. All fertilizers contained perchlorate: nitrogenous fertilizers (mean: 32.6 mg kg-1), NPK (mean: 12.6 mg kg-1), non-nitrogenous fertilizers (mean: 10.2 mg kg-1) and phosphates (mean: 11.5 mg kg-1). Only one type of nitrogenous fertilizer (KNO3: 95.3 mg kg-1) exceeded the international regulation limit (50 mg kg-1). For two agronomic practices, the content of perchlorate in lettuce increased as the fertilizer application rate increased, with fertigation promoting a more significant accumulation. However, the concentrations generally remained below regulatory values. Our results suggest that fertilizers constitute an important source of perchlorate in soils.

Field study on the uptake, accumulation and risk assessment of perchlorate in a soil-chard/spinach system: Impact of agronomic practices and fertilization.

The application of excessive fertilizer represents a primary source of entry for perchlorate into crop systems and thus has raised widespread concern regarding food safety. Several studies have reported the occurrence of perchlorate in vegetables. However, limited information is available on the fate of perchlorate in the soil-plant system. In this study, we performed field experiments to evaluate the effects of the application rate of Chilean nitrate fertilizer and the type of fertilization (manual or fertigation) on the uptake of perchlorate by plants grown in open fields. Interestingly, in the control, chard and spinach accumulated 21.3 and 25.9 µg kg-1, respectively. For both agronomic practices, the content of perchlorate in chard and spinach increased as the fertilizer application rate increased, with fertigation promoting more significant accumulations. Spinach accumulated almost two times more perchlorate than chard for all treatments; however, the concentrations generally remained below regulatory values. The intake of spinach and chard presented a low risk to human health for all age groups. These findings enhance our understanding of the environmental impact of the use of fertilizers in agriculture and food safety.

Effect of cadmium on phenolic compounds, antioxidant enzyme activity and oxidative stress in blueberry (Vaccinium corymbosum L.) plantlets grown in vitro.

Cadmium (Cd(2+)) can affect plant growth due to its mobility and toxicity. We evaluated the effects of Cd(2+) on the production of phenolic compounds and antioxidant response of Vaccinium corymbosum L. Plantlets were exposed to Cd(2+) at 50 and 100µM for 7, 14 and 21 days. Accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and the antioxidant enzyme SOD was determined. The profile of phenolic compounds was evaluated using LC-MS. The antioxidant activity was measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the ferric reducing antioxidant power test (FRAP). Cd(2+) increased the content of MDA, with the highest increase at 14 days. The presence of Cd(2+) resulted in changes in phenolic compounds. The main phenolic compound found in blueberry plantlets was chlorogenic acid, whose abundance increased with the addition of Cd(2+) to the medium. The changes in the composition of phenolic compounds showed a positive correlation with the antioxidant activity measured using FRAP. Our results suggest that blueberry plantlets produced phenolic compounds with reducing capacity as a selective mechanism triggered by the highest activity of Cd(2+).