Dioxins In Soil Research Articles

Levels and risk assessment of dl-PCBs and dioxins in soils surrounded by cement plants from industrial areas of Colombia and Spain

This study investigates the concentrations of 17 PCDD/Fs and 12 dl-PCBs congeners in soil samples collected from industrial areas in Cartagena de Indias (Colombia) and Valencia (Spain). The aim is to assess the characteristic distribution patterns and the potential risk around cement plants within the selected locations, addressing the lack of data on PCDD/Fs and dl-PCBs in soils from the two studied areas. Soil samples were analysed using gas chromatography coupled to high-resolution mass spectrometry (GC-HRMS). The PCDD/Fs concentrations varied from 0.01 pg g−1 dw to 520.43 pg g−1 dw in Colombia and from 0.01 pg g−1 dw to 150.48 pg g−1 dw in Spain. For dl-PCBs, levels ranged from 0.03 pg g−1 dw to 1611.83 pg g−1 dw in Colombia and from 0.06 to 189.64 pg g−1 dw in Spain. Despite the differences observed in concentration terms between the two areas studied, the same pattern of congeners was observed. The hazard index (HI) values for exposure of adults and children in soil were, in overall, smaller than one (HI < 1), while the total cancer risk (TCR) values exceeded the acceptable risk value of 10−6, which indicate probable non-carcinogenic and carcinogenic risks resulting from exposure to PCDD/Fs and dl-PCBs in these areas. The ecological risk was assessed using the Contamination Factor (CF) and the Ecological Risk Index (ERI), revealing significant contamination in the studied areas.

Baseline Soil Dioxin Levels from Sites Where Municipal Solid Waste Incineration Construction Is Planned throughout China: Characteristics, Sources and Risk Assessment

The determination of baseline dioxins levels in soils is fundamental for the quantitative assessment of the net environmental and health impacts of municipal solid waste (MSW) incineration plants, which remains unexplored. Therefore, this study develops a Chinese baseline soil dioxins database (covering 918 soil samples from 292 pre-construction MSW incineration plants nationwide during 2016–2020) to thoroughly explore the baseline contamination characteristics and health risks of dioxins in soils. The empirical results show that (1) for concentration levels, the baseline international toxic equivalency (I-TEQ) concentrations vary from 0.0015 to 32 ng I-TEQ/kg, which are close to or even lower than those in most existing studies and show significant heterogeneity across provinces; (2) for dioxins homolog, highly chlorinated dioxins (i.e., PCDDs) are the dominant contributor to the total dioxins in soils (contributing 54.30% of the total I-TEQ concentrations), implying that dioxins in baseline soils often have an atmospheric fingerprint; and (3) for health risks, the carcinogenic risk and non-carcinogenic risk of dioxins in soils are mostly below acceptable levels, close to or even lower than the results of previous studies. Despite these results being considered as quite preliminary, they have certain implications for local authorities. Future studies can expand the size of the database and the generalizability of the results, and if necessary, establish a long-term dynamic monitoring of dioxins in soils for systematically evaluating the net impact of MSW incineration on environment and human health.

In-silico analysis of atmospheric diffusion, crop planting degrading scheme, and health risk of dioxins from a domestic waste incineration plant.

Based on a domestic waste incineration power generation project, the dioxin emission from the waste incineration plant (WIP), phytoextraction and microbial degradation of dioxins, and dioxins human health risks reduction were investigated through in-silico methods. Based on the dioxins concentrations in soil (9.97×10-9-7.00×10-5ng/g) predicted by atmospheric dispersion model system and the Level-III fugacity model, planting schemes under different wind directions were designed considering the dioxin absorption capacity and the economic benefits for crops (i.e., barley, peanut, pea, maize and wheat). The dioxins in soils can be further degraded by five crops' rhizosphere microorganisms and fertilizers, simulated through molecular dynamic simulations. The enhanced degradation rates of dioxin by rhizosphere microorganisms of five crops reached 15.70%-28.66%. Finally, healthy dietary plans were developed to reduce the risk of dioxin exposure to the sensitive populations living around WIP. Results showed that the consumption of maize, fungus, mushroom and bamboo fungus could effectively reduce dioxins toxicity to humans by 58.13%. The systematic approach developed in this study provided theoretical support for soil remediation and human health risk control of dioxins-contaminated sites.

A Review of Soil Contaminated with Dioxins and Biodegradation Technologies: Current Status and Future Prospects

This article provides a comprehensive assessment of dioxins contaminating the soil and evaluates the bioremediation technology currently being widely used, and also offers recommendations for future prospects. Soil pollution containing dioxins is extremely toxic and hazardous to human health and the environment. Dioxin concentrations in soils around the world are caused by a variety of sources and outcomes, but the main sources are from the consequences of war and human activities. Bioremediation technology (bioaugmentation, biostimulation, and phytoremediation) is considered an optimal and environmentally friendly technology, with the goal of applying native microbial communities and using plant species with a high biomass to treat contaminated dioxins in soil. The powerful bioremediation system is the growth of microorganisms that contribute to the increased mutualistic and competitive relationships between different strains of microorganisms. Although biological treatment technology can thoroughly treat contaminated dioxins in soil with high efficiency, the amount of gas generated and Cl radicals dispersed after the treatment process remains high. Further research on the subject is required to provide stricter control over the outputs noted in this study.

Kaolinitic clays as a potential source of dioxins in the Noosa River catchment, Queensland, Australia

Environmental context Dioxins have been found along the east coast of Australia in agricultural areas where there is no obvious source of dioxins. These dioxins have an unusual signature that does not match common industrial sources, but it has been suggested that they may be associated with pesticide use. This study found a strong correlation between dioxins with this unique signature and the amount of a kaolinitic clay in the sediments sampled. Abstract The presence, concentrations and profiles of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in sediment were investigated in this study with the aim of determining whether dioxin-like compounds were present and, if found, a likely source could be deduced. The sampled catchment lies within an area of high conservation value. Sediments from seven lake sites were sampled as possible sinks for any contamination from historical pesticide use. PCDD/Fs were measured in all the lake sediments. The 2,3,7,8-substituted congener profile was dominated by octachlorodibenzo-p-dioxin (OCDD) with furans at or below the limit of detection, a profile that has been associated with kaolinitic clays from around the world. A strong and significant correlation was found between the total dioxin concentration and the percentage of kaolinitic clay in the sediments. The lack of furans in the 2,3,7,8-substituted PCDD/F profile indicates pesticides or pentachlorophenol (PCP) are unlikely to be the source in the catchment. Further, the concentration of total dioxins and OCDD tended to be higher than those measured outside the study area, even though, overall, the study area is likely to have had less pesticide use than the other intensive agricultural areas previously studied. The results presented in this paper indicate that caution should taken when attributing the presence of dioxins in soil and sediment to anthropogenic sources.

Improvement of reporter gene assay for highly sensitive dioxin detection using protoplastic yeast with inactivation of CWP and PDR genes.

A yeast reporter gene assay system with improved performance for dioxin detection was established. Since yeast reporter gene assays are relatively simple, easy to handle, and inexpensive, they have been used for various assessments of environmental contaminants. We previously constructed a yeast assay strain expressing the aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (Arnt) carrying the lacZ reporter gene, for detection of dioxins. In the present study, genes encoding cell wall mannoproteins and ATP-binding cassette transporters in the yeast assay strains were deleted in order to increase the substance influx and prevent its efflux. We also established an assay procedure for protoplasts of these yeasts. These modifications improved the detection limit 40-fold and reduced the duration of the assay by 40%. By combining the yeast protoplast and a rapid sample preparation technique using disposal multilayer solid-phase extraction columns to remove unintended aryl hydrocarbons, this yeast reporter gene assay system detected the ligand activities of dioxins and related compounds in 1g of forest soil containing dioxins at a concentration 10 times lower than the Japanese environmental standard for dioxins in soil.

Free-range chicken eggs as a bioindicator of dioxin contamination in Vietnam, including long-term Agent Orange impact

Abstract PCDD/Fs contamination of free-range chicken eggs and soils from private Vietnam households was studied. The possibility of using free-range eggs as bio-indicators of dioxin contamination was considered as the soil-chicken-egg exposure pathway is considered to be the most sensitive exposure pathway of dioxins in soils to humans. A large territory from Dong Nai province in the south to Lao Cai province in the north was covered by the research. All analyses were performed by HRGC-HRMS method. PCDD/Fs levels in eggs from the majority of southern households exceeded the EC limit for eggs and egg products (2.5 pg WHO-TEQ2005 g−1 lipid). Total TEQs ranged from 0.4 to 361 pg WHO-TEQ2005 g−1 lipid in eggs and from 0.1 to 1272 pg WHO-TEQ2005/g in soil. 2,3,7,8-TCDD contribution was statistically significantly higher in both eggs and soils in sprayed with Agent Orange areas, indicating its long-term impact. In order to assess within site variation, a total of 62 individual eggs from 14 private households were analyzed. Mean relative standard deviation of total TEQ values in individual eggs within the separate households was 27%. Rather good correlation of PCDD/Fs concentration in eggs and respective soils was observed for all dioxin congeners and for hexa- and hepta-furans (except for 1,2,3,7,8,9-HxCDF). Higher bioaccumulation for lower chlorinated congeners was confirmed. The current study of using eggs as bio-indicators for large POPs contaminated sites may be suggested as a policy approach to evaluate human exposure to dioxin/POPs contaminated sites for known or suspected contaminated areas.

Assessing ecotoxicological effects of 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, and 2,3,4,7,8-PeCDF in soil using Allivibrio fischeri

The toxic effect of dioxins and dioxin-like compounds have largely been studied using in vivo techniques; however, in vivo studies can be limited when rapid screening is required. Microtox® can be used as a rapid ecotoxicity assessment tool for dioxins in the environment, but studies on the assessment of dioxins and dioxin-like compounds using bioluminescent bacteria Allivibrio fischeri are limited. This study investigated the potential of using A. fischeri for assessing different dioxins and dioxin-like compounds, and the toxic effects of soils contaminated with dioxins and dioxin-like compounds were tested using different fractions of dioxins in soil to determine the appropriate way of assessing the toxic effects of contaminated soils. The results show that A. fischeri can potentially be used as a test species for rapidly evaluating toxic effects of dioxins and dioxin-like compounds in the environment. With the soil used in this study, the toxic effects of the water extracts (i.e., mobile fraction of dioxins) and the soil slurries (i.e., bioavailable fraction of dioxins) were similar to that of the controls. This suggests that the toxicity assessment of the organic extracts (i.e., total amount of dioxins) can be inappropriate in a managerial perspective, as the mobile or bioavailable fraction of contaminants in soils is often more of concern than the total amount of contaminants present in soils. Overall, when A. fischeri are to be used for a rapid toxicity assessment of dioxins-contaminated soils, different fractions of dioxins need to be assessed for better management of the contaminated soils.

A Study on the Physicochemical Properties of Different Post-Process Wastes from Thermal Processes

The main aim of the article is determinate the safety for use the anthropogenic raw materials such as ashes and slags produced in waste incineration plants and possibilities of they using for manufacturing building materials. The article presents the results of research on physicochemical properties of ashes and slags produced in waste incineration plants. The research methods used were: water leaching, radioactivity, dioxins and furans content, oxide and phase composition. The major treatment for investigated waste is a high level of leaching of harmful substances and the content of dioxins and furans. It is necessary to take appropriate measures to develop procedures for safe processing and storage of this type of materials. As shown in the research, ashes from the two investigated waste incinerators do not meet the requirements for leaching levels for hazardous waste landfills. These wastes must undergo processing to reduce to an appropriate level of leaching. Referring to the sum of dioxins in soils in urban areas, which is from 5 to 10 ng / kg, it can be stated that the waste tested contains very high dioxin contents and is hazardous waste. Working with this kind of waste requires special precautions. The ashes from waste incineration plants exceed this limit several dozen times (eg 221 ng I-TEQ / kg). Due to very high values of leaching and dioxin content in the raw materials, even the rinsing process does not guarantee the possibility of obtaining waste that could be stored in hazardous waste landfills. The article suggests the further way of safety processing this kind of materials.

Impact of environmental pollution on PCDD/F and PCB bioaccumulation in game animals

Elucidation of the relationship between the levels of 35 individual dioxins and polychlorinated biphenyl congeners in environmental samples (pine needles, leaves, grass and soil), and their bioaccumulation in the muscles of two game animal families (Cervidae and Suidae) was the aim of the research. Comparative studies were performed in four industrially degraded regions with various types of heavy industry and in an agricultural region with a tourism industry. The content of pollutants was determined by the isotopic dilution method using high resolution gas chromatography coupled with high resolution mass spectrometry. The polychlorinated dibenzodioxins/furan and PCB profiles in plants, soil and animal tissues varied by region and were related to the indigenous industry. The presence of characteristic congeners of particular industrial sectors was found. The animal tissue congeners were a reflection of the types and levels found in soil and plants. Independently of the region, deer tissue had almost twice the concentration of PCDD/F/DL-PCBs compared to boars, but the converse was true for NDL-PCBs. Spearman’s statistical test showed strong correlations between pine needle, leaf, grass and soil dioxin and dioxin-like PCB levels and concentrations of these in the tissues of both species. Coefficients of bioaccumulation in deer muscles (BAF) calculated for all regions varied considerably and they were significantly higher for wild boars. BAF decreased with increasing number of chlorine atoms in the dioxin and furan molecule. The highest congener values were for 2,3,7,8-tetrachlorodibenzodioxin, 1,2,3,7,8-pentachlorodibenzodioxin, 2,3,7,8-tetrachlorodibenzofuran and 2,3,4,7,8-pentachlorodibenzofuran in both kinds of muscle regardless of the region. The levels of pollutants, types of pollutants, and their relative abundance in tissues of deer and boar reflected their surrounding environment and local pollutant emitters.

Gas chromatography–triple quadrupole mass spectrometry analysis of dioxins in soil

The applicability of gas chromatography–triple quadrupole mass spectrometry (GC–MS/MS) for determination of dioxins in soil was investigated. The analytical method was validated based on US Environmental Protection Agency (EPA) Method 1613 and European Union (EU) Regulation No. 709/2014 for selectivity, linearity of sensitivity, and instrumental limits of quantification (iLOQs). Method development commenced with determination of retention times for 17 native polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) and selection of characteristic ions from GC–MS/MS spectra. The linearity was measured using 1613 standard solutions (CS1–CS5) containing 0.5 to 200 ng/mL tetrachlorodibenzo-p-dioxin/furan (TCDD/F) congeners, 2.5 to 1000 ng/mL pentachlorodibenzo-p-dioxin/furan (PeCDD/F) to heptachlorodibenzo-p-dioxin/furan (HpCDD/F) congeners, and 20 to 2000 ng/mL octachlorodibenzo-p-dioxin/furan (OCDD/F) congeners. The correlation coefficient (R2) values ranged between 0.9990 and 0.9999, and the iLOQ values ranged from 0.052 to 0.350 pg/μL for TCDD/F congeners, with a relative standard deviation of 2.7–9.6%. The entire analytical method was verified by analysis of certified reference materials (BCR-529 and BCR-530), and the recoveries were 71.79–103.87% and 81.50–103.12%, respectively. Thus, the GC–MS/MS system provides an alternative to GC–high-resolution MS for the simultaneous determination of TCDD/F congeners in soil.

An AhR-Luciferase Adenovirus Infection System for Rapid Screening of Dioxins in Soils.

Our goal was to develop a fast-screening method for measuring dioxin levels in soils. The adenovirus (Ad)-dioxin-responsive (DR) bioassay system (AdEasy-6XDRE-TATA-Luc) combined with a fast-cleanup system was examined under conventional conditions (i.e., with incubation at 37°C) and three alternative conditions [incubation at 37°C with addition of phorbol-12-myristate-13-acetate (PMA), incubation at 33°C, and incubation at 33°C with addition of PMA]. The best conditions for carrying out the Ad-DR bioassay was 33°C and no addition of PMA. The background level of soil dioxins determined by the chemical assay [6.49 ng I-TEQ/kg dry weight (dw)] was well correlated (Pearson's r = 0.873, p < 0.001) with that by the Ad-DR bioassay [expressed in ng bioanalytical equivalents (BEQ) 81.1 ng BEQ/kg dw] (n = 17). When surveyed in contaminated soil samples (n = 114) from industrial areas by the Ad-DR bioassay, dioxin levels were 117, 102, 98.5, and 112 ng BEQ/kg dw, respectively, in northern, central, southern, and eastern Taiwan.

Vertical distribution of dioxins in soil of Bien Hoa airbase, Vietnam.

Bien Hoa airbase is a known dioxin-contaminated hotspot in Vietnam. The contamination occurred during the Vietnam War at the site where dioxins were transported, stored, sprayed, and spilled in the area. Dioxins, which are cancer inducing substances, may transfer from the soil to food crops and finally to human beings living around the area. Many surveys of dioxins in soil, water, organisms, and human have been carried out in this study area since 2002. In this paper vertical distribution of dioxins in undisturbed soil cores were examined. Twelve soil samples from three drilled cores were collected to analyze dioxin levels according to the standard Japanese analytical method. The results showed that the toxicity equivalency quantity (TEQ) in one soil sample at a depth of 2.6 m reached 3,300 pg-TEQ/g-dw. High TEQs were also observed in the clay layer. This anomaly of dioxin concentrations could be attributed to the affinity of dioxins for the clay layer. The isomer patterns in the soils were different from those in the soil of Hokkaido in that 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD) was the most dominant in the soil sample. This indicates that the dioxins originate from a defoliant Agent Orange disposed at the site after the Vietnam War.

Traceability of polychlorinated dibenzo-dioxins/furans pollutants in soil and their ecotoxicological effects on genetics, functions and composition of bacterial community

Dioxins (PCDD/Fs) are persistent organic pollutants. Their accumulation in soil is a crucial step in their transmission through the ecosystem. Traceability of dioxin in soil was evaluated in four sites A, B, C and D considered as potential industrial PCDD/Fs sources in Syria. Our results showed that the highest pollution with dioxin (⩾50 ppt) was found in site C (vicinity of Homs refinery). In parallel, analysis of physicochemical proprieties and bacterial density of soil samples were carried out. Bacterial density differed significantly among samples between 68×104 and 64×106CFUg−1DW. Analysis of 16S rRNA encoding sequences showed that the genus Bacillus was the most abundant (74.7%) in all samples, followed by the genera Arthrobacter and Klebsiella with 5.2% and 4.7%, respectively. The genera Microbacterium, Pantoea, Pseudomonas, Enterobacter and Exiguobacterium formed between 2.1% and 2.6%. Cellulomonas, Kocuria, Lysinibacillus, Staphylococcus and Streptomyces were in a minority (0.5–1%). The bacterial richness and biodiversity, estimated by DMg and H′ index, were highest in the heavily polluted site. Molecular screening for angular dioxygenase (AD α-subunit) and the cytochrome P450 (CYPBM3) genes, led to identification of 41 strains as AD-positive and 31 strains as CYPBM3-positive. RT-real-time PCR analysis showed a significant abundance of AD α-subunit transcript in the heavily dioxin-polluted soils, while the expression of CYPBM3 was highest in the moderately polluted soils. Our results illustrate the microbial diversity and functionality in soil exposed to dioxin pollution. Identification of dioxin-degrading bacteria from polluted sites should allow bioremediation to be carried out.

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry using a femtosecond laser

A laser can be used for the selective excitation and subsequent ionization of a molecule with an absorption band at the laser wavelength. This technique of multiphoton ionization (MPI), when combined with time-of-flight mass spectrometry (TOF-MS), permits the efficient detection of induced ions in mass analysis. This combination of MPI/TOF-MS can be coupled with gas chromatography (GC) to achieve even more enhanced selectivity. Thus, GC/MPI/TOF-MS can be employed for trace analysis of samples containing numerous chemical species. A variety of laser sources have been used for this purpose. Since molecules that are classified as environmental pollutants frequently contain chlorine and bromine atoms, the lifetime of the excited state can be decreased by energy transfer from the singlet to triplet levels by spin-orbit interaction. A high-power femtosecond laser with a pulse width shorter than the lifetime of the analyte molecule provides femtogram or even subfemtogram detection limits, which have not yet been achieved using the most sensitive high-resolution double-focus sector-type mass spectrometers. Numerous environmental pollutants such as dioxins in soils and pesticides in foods have been successfully quantified using GC/MPI/TOF-MS, and this technique has proven itself to be a useful and practical method for trace analysis.

Application of an aryl hydrocarbon receptor based screening assay for assessing U.S. EPA draft remediation goals for dioxin in soil and sediment samples

An aryl hydrocarbon receptor (AhR)-based, real-time polymerase chain reaction (PCR) assay (Procept®) was used to determine dioxin-like compounds in soil and sediment samples from seven sites known to be contaminated by dioxin and related compounds. The biological equivalent quotient (BEQ) generated by the Procept® assay was compared with toxicity equivalent (TEQ) measurements by isotope dilution gas chromatography-mass spectrometry (GC-MS). This research demonstrated that the Procept® assay has several limitations, when compared with GC-MS, including poorer detection limits and precision, and increased sensitivity to a wide range of AhR agonists and antagonists, such as polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCBs). However, results indicate that the Procept® assay can be used as an effective screening technique for dioxin-like compounds at the EPA draft recommended interim preliminary remediation level for dioxin in soils of 72 pg/g TEQ.

An Improved AhR Reporter Gene Assay for Analyzing Dioxins in Soil, Sediment and Fish

Our goal was to develop a fast-screening bioassay to determine dioxin levels in the environmental and biological samples from dioxin-contaminated areas. Our original dioxin-responsive-element (DRE)-driven luciferase bioassay (using Huh7-DRE-Luc cells) was modified by reducing the incubation temperature of the cell culture from 37 to 35°C and by adding phorbol-12-myristate-13-acetate, and the modified bioassay was used to examine samples from soil, sediment, and fish. The results of this bioassay were shown to be significantly related to those of the high-resolution gas chromatography/high-resolution mass spectrometry assay of dioxins. The correlative equation was: log (PCDD/Fs I-TEQs) = 1.19 × log (BEQs) - 1.15 with R(2) = 0.95 (p < 0.001).

Distribution patterns and major sources of dioxins in soils of the Changsha-Zhuzhou-Xiangtan urban agglomeration, China

Surface soils from an industrial base, the Changsha-Zhuzhou-Xiangtan urban agglomeration in central China were analyzed for 2378-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The PCDD/F concentrations ranged from 268 to 7510pgg−1 dry weight (dw), 72% of which were above the U.S. guideline value (1000pgg−1). It was found that octachlorodibenzo-p-dioxin (OCDD) was the most dominant congener accounting for 78.4–99.3% of the total PCDD/Fs, which was consistent with the PCDD/F profiles reported in other Asian countries. It is recommended that the four major sources of PCDD/Fs in the region can be diesel-fuel vehicles, open straw burning, mass burn-water wall (MB-WW), pentachlorophenate (PCP)/PCP-Na and boilers-hazardous waste incineration. This study is one of the few studies with a focus on the PCDD/F pollution in central China, providing evidences for establishing priorities in reduction of ecological risks posed by PCDD/Fs in central China and elsewhere.

Potential impact of fertilization practices on human dietary intake of dioxins in Belgium

Dioxins can enter the food chain at any stage, including crop fertilization. Therefore, we developed a simple method for estimating the introduction of dioxins in the food chain according to various fertilization practices. Using dioxin's contamination data taken from the literature, we estimated that fertilization accounts for approximately 20% of the dioxin inputs on agricultural soils at country scale. For the estimations at the field scale, 6 fertilization scenarios were considered: sludge, compost, digestate, manure, mineral fertilizers, and a common fertilization scenario that corresponds to an average situation in Belgium and combines mineral and organic fertilizers. According to our first estimations, mineral fertilizers, common fertilization practices or manure bring less than 1ngTEQ/m² while atmospheric deposition or digestate bring between 1 and 3ngTEQ/m² and sludge or compost bring more than 3ng TEQ/m². The use of solid fertilizers could potentially increase the dioxin levels in the 30 cm agricultural soil layer by 0 to ~1.5% per year (up to ~9% for the 5cm thick surface layer). For animals, the increase in dioxin ingestion linked to the fertilization practices is lower than 1% for most scenarios with the exception of the compost scenario. Increases in human dietary intake of dioxin are estimated to be lower than 1% for conventional rearing methods (i.e. grazing animals are reared outdoor while pigs and poultry are reared indoor). Spraying liquid fertilizers on meadows and fodder crops, even if very limited in practice, deserves much more attention because this application method could theoretically lead to higher dioxin's intake by livestock (from 6 to ~300%). Considering an average half-life of dioxins in soils of 13years, it appears that the risks of accumulation in soils and in the food chain are negligible for the various fertilization scenarios.

Human Exposure from Dioxins in Soil

Dioxins are a family of chemical compounds that has received considerable attention, both historically and currently. This article reviews scientific field studies that examine the relationship between living on soil contaminated with dioxins and the level of dioxins in people's serum, with an emphasis on the University of Michigan Dioxin Exposure Study (UMDES), the largest and most comprehensive study of its kind. These studies conclude that the levels of dioxins in serum are most strongly correlated with age, gender, body mass index, weight loss, breast feeding, and smoking. Levels of dioxins in soil are not significant predictors for dioxin concentrations in serum. The increase in serum dioxin levels that is seen with age results from historic exposure and does not represent ongoing exposure. Based on the scientific field studies conducted to date, it appears that, in the absence of the consumption of contaminated animal products, there is little evidence of ongoing exposure from contaminated soil.