RCRA toxicity characterization of discarded electronic devices

The potential for discarded electronic devices to be classified as toxicity characteristic (TC) hazardous waste under provisions of the Resource Conservation and Recovery Act (RCRA) using the toxicity characteristic leaching procedure (TCLP) was examined. The regulatory TCLP method and two modified TCLP methods (in which devices were disassembled and leached in or near entirety) were utilized. Lead was the only element found to leach at concentrations greater than its TC limit (5 mg/L). Thirteen different types of electronic devices were tested using either the standard TCLP or modified versions. Every device type leached lead above 5 mg/L in at least one test and most devices leached lead above the TC limit in a majority of cases. Smaller devices that contained larger amounts of plastic and smaller amounts of ferrous metal (e.g., cellular phones, remote controls) tended to leach lead above the TC limit at a greater frequency than devices with more ferrous metal (e.g., computer CPUs, printers).     

Arsenic leaching from mulch made from recycled construction and demolition wood and impacts of iron-oxide colorants

Mulch made from recycled construction and demolition (C&D) wood has been reported to contain elevated levels of arsenic from inadvertent inclusion of chromated copper arsenate (CCA)-treated wood. Such mulch is also commonly colored with iron oxide, a compound known to bind arsenic. The objectives of this study were to quantify the releases of arsenic from mulch made from C&D wood, to evaluate the impacts of an iron-oxide colorant in potentially decreasing arsenic leaching rates, and to evaluate the relative significance of additional variables on leachate concentrations. Atotal of 3 sets of mulch samples (0%, 5%, or 100% CCA-treated wood) were prepared containing a sample either with or without colorant addition. Each sample was subjected to two tests: a field leaching test and the Synthetic Precipitation Leaching Procedure (SPLP). Results showed that arsenic concentrations in the field leachate from the 0% treated wood mulches were consistently low (<0.003-0.013 mg/L) whereas leachates from 5 and 100% treated wood mulches were characterized by higher arsenic concentrations (0.059-2.23 mg/L for 5%; 0.711-22.7 mg/L for 100%). The mass of arsenic leached from the field samples during the 1-year monitoring period was between 10 and 15% of the initial mass of arsenic. The colorant reduced the leaching of arsenic by more than 20% for the field leachate and 50% for the SPLP leachate, on average. However, the study showed that the effect may not last for long periods. Besides colorant addition other factors were observed to affect the amount of arsenic leached from contaminated mulch. These include the proportion of CCA-treated wood in the mulch, time, and pH of rainfall.     

Arsenic speciation of solvent-extracted leachate from new and weathered CCA-treated wood

For the past 60 yr, chromate-copper-arsenate (CCA) has been used to pressure-treat millions of cubic meters of wood in the United States for the construction of many outdoor structures. Leaching of arsenic from these structures is a possible health concern as there exists the potential for soil and groundwater contamination. While previous studies have focused on total arsenic concentrations leaching from CCA-treated wood, information pertaining to the speciation of arsenic leached is limited. Since arsenic toxicity is dependent upon speciation, the objective of this study was to identify and quantify arsenic species leaching from new and weathered CCA-treated wood and CCA-treated wood ash. Solvent-extraction experiments were carried out by subjecting the treated wood and the ash to solvents of varying pH values, solvents defined in the EPA's Synthetic Precipitation Leaching Procedure (SPLP) and Toxicity Characteristic Leaching Procedure (TCLP), rainwater, deionized water, and seawater. The generated leachates were analyzed for inorganic As(III) and As(V) and the organoarsenic species, monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA), using high-performance liquid chromatography followed by hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS). Only the inorganic species were detected in any of the wood leachates; no organoarsenic species were found. Inorganic As(V) was the major detectable species leaching from both new and weathered wood. The weathered wood leached relatively more overall arsenic and was attributed to increased inorganic As(III) leaching. The greater presence of As(III) in the weathered wood samples as compared to the new wood samples may be due to natural chemical and biological transformations during the weathering process. CCA-treated wood ash leached more arsenic than unburned wood using the SPLP and TCLP, and ash samples leached more inorganic As(III) than the unburned counterparts. Increased leaching was due to higher concentrations of arsenic within the ash and to the conversion of some As(V) to As(III) during combustion.     

Relative leaching and aquatic toxicity of pressure-treated wood products using batch leaching tests

Size-reduced samples of southern yellow pine dimensional lumber, each treated with one of five different waterborne chemical preservatives, were leached using 18-h batch leaching tests. The wood preservatives included chromated copper arsenate (CCA), alkaline copper quaternary, copper boron azole, copper citrate, and copper dimethyldithiocarbamate. An unpreserved wood sample was tested as well. The batch leaching tests followed methodology prescribed in the U.S. Environmental Protection Agency toxicity characteristic leaching procedure (TCLP). The wood samples were first size-reduced and then leached using four different leaching solutions (synthetic landfill leachate, synthetic rainwater, deionized water, and synthetic seawater). CCA-treated wood leached greater concentrations of arsenic and copper relative to chromium, with copper leaching more with the TCLP and synthetic seawater. Copper leached at greater concentrations from the arsenic-free preservatives relative to CCA. Arsenic leached from CCA-treated wood at concentrations above the U.S. federal toxicity characteristic limit (5 mg/L). All of the arsenic-free alternatives displayed a greater degree of aquatic toxicity compared to CCA. Invertebrate and algal assays were more sensitive than Microtox. Examination of the relative leaching of the preservative compounds indicated that the arsenic-free preservatives were advantageous over CCA with respect to waste disposal and soil contamination issues but potentially posed a greater risk to aquatic ecosystems.     

Redox transformations of arsenic and iron in water treatment sludge during aging and TCLP extraction

Laboratory experiments and modeling studies were performed to investigate the redox transformations of arsenic and iron in water treatment sludge during aging, and to evaluate the impact of those transformations on the leachability of arsenic determined with the U.S. EPA toxicity characteristic leaching procedure (TCLP). When the backwash suspension samples collected from a California surface water treatment plant were aged in closed containers for a few weeks, soluble arsenic increased from less than 5 microg/L to as high as 700 microg/L and then decreased dramatically because of biotic reduction of arsenate [As(V)], ferric oxyhydroxide, and sulfate. The experimental results and the thermodynamic models showed that arsenic mobility can be divided into three redox zones: (a) an adsorption zone at pe > 0, which is characterized by strong adsorption of As(V) on ferric oxyhydroxide; (b) a mobilization (transition) zone at -4.0 < pe < 0, where arsenic is released because of reduction of ferric oxyhydroxide to ferrous iron and As(V) to arsenite [As(III)]; and (c) a reductive fixation zone at pe < -4.0, where arsenic is immobilized by pyrite and other reduced solid phases. The TCLP substantially underestimated the leachability of arsenic in the anoxic sludge collected from sludge ponds because of the oxidation of Fe(II) and As(III) by oxygen. The leaching test should be performed in zero-headspace vessels or under nitrogen to minimize the transformations of the redox-sensitive chemical species.     

Arsenic leachability in water treatment adsorbents

Arsenic leachability in water treatment adsorbents was studied using batch leaching tests, surface complexation modeling and extended X-ray absorption fine structure (EXAFS) spectroscopy. Spent adsorbents were collected from five pilot-scale filters that were tested for removal of arsenic from groundwater in Southern New Jersey. The spent media included granular ferric hydroxide (GFH), granular ferric oxide, titanium dioxide, activated alumina, and modified activated alumina. The As leachability determined with the Toxicity Characteristic Leaching Procedure (TCLP, 0.1 M acetate solution) was below 180 microg L(-1) for all spent media. The leachate As concentration in the California Waste Extraction Test (0.2 M citrate solution) was more than 10 times higher than that in the TCLP and reached as high as 6650 microg L(-1) in the spent GFH sample. The EXAFS results indicate that As forms inner-sphere bidentate binuclear surface complexes on all five adsorbent surfaces. The As adsorption/desorption behaviors in each media were described with the charge distribution multisite complexation model. This study improved the understanding of As bonding structures on adsorptive media surfaces and As leaching behavior for different adsorbents.     

Leaching of lead from computer printed wire boards and cathode ray tubes by municipal solid waste landfill leachates

The proper management of discarded electronic devices (E-waste) is an important issue for solid waste professionals because of the magnitude of the waste stream and because these devices often contain a variety of toxic metals (e.g., lead). While recycling of E-waste is developing, much of this waste stream is disposed in landfills. Leaching tests are frequently used to characterize the potential of a solid waste to leach when disposed in a landfill. In the United States, the Toxicity Characteristic Leaching Procedure (TCLP) is used to determine whether a solid waste is a hazardous waste by the toxicity characteristic. The TCLP is designed to simulate worse-case leaching in a landfill environment where the waste is co-disposed with municipal solid waste (MSW). While the TCLP is a required analysis from a regulatory perspective, the leachate concentrations measured may not accurately reflect the concentrations observed under typical landfill conditions. Another method that can be performed to assess the degree a pollutant might leach from a waste in a landfill is to use actual landfill leachate as the leaching solution. In this study, two lead-containing components found in electronic devices (printed wire boards from computers and cathode ray tubes from computers and televisions) were leached using the TCLP and leachates from 11 Florida landfills. California's Waste Extraction Test (WET) and the Synthetic Precipitation Leaching Procedure were also performed. The results indicated that the extractions using MSW landfill leachates resulted in lower lead concentrations than those by the TCLP. The pH of the leaching solution and the ability of the organic acids in the TCLP and WET to complex with the lead are factors that regulate the amount of lead leached.     

Chemical stability of acid rock drainage treatment sludge and implications for sludge management

To assess the chemical stability of sludges generated by neutralizing acid rock drainage (ARD) with alkaline reagents, synthetic ARD was treated with hydrated lime (batch and high-density sludge process), limestone, and two proprietary reagents (KB-1 and Bauxsol). The amorphous metal hydroxide sludge produced was leached using deionized water, U.S. EPA methods (toxicity characteristic leaching procedure, synthetic precipitation leaching procedure), and the new strong acid leach test (SALT), which leaches the sludge with a series of sulfuric acid extractant solutions; the pH decreases by approximately 1 pH unit with each test, until the final pH is approximately 2. Sludges precipitated by all reagents had very similar leachabilities except for KB-1 and Bauxsol, which released more aluminum. SALT showed that lowering the pH of the leaching solution mobilized more metals from the sludges. Iron, aluminum, copper, and zinc began to leach at pH 2.5-3, approximately 4.5, approximately 5.5, and 6-6.5, respectively. The leachability of ARD treatment sludges is determined by the final pH of the leachate. A higher neutralization potential (e.g., a greater content of unreacted neutralizing agent) makes sludges inherently more chemically stable. Thus, when ARD or any acidic metalliferous wastewater is treated, a choice must be made between efficient reagent use and resistance to acid attack.     

Anion leaching from refinery oily sludge and ash from incineration of oily sludge stabilized/solidified with cement. Part I. Experimental results

This paper presents the leaching behavior of anions (SO4(2-) and CrO4(2-)) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, 142.5 and 1142.5. Anion leaching was examined using a 5-step sequential toxicity characteristic leaching procedure (TCLP) test. A single TCLP extraction resulted in limited sulfate release (<50 mg/L) for s/s ash and significant sulfate release (<850 mg/L) for s/s oily sludge. Chromate release was <1 mg/L for s/s ash and nondetectable for s/s oily sludge. The sequential TCLP tests resulted in increased leaching for both sulfate and chromate. In general,the increase of liquid-to-solid ratio (TCLP leachant-to-waste ratio) resulted in increased leaching of sulfate from solidified samples compared to untreated oily sludge, ash and cement. In contrast, chromate leaching decreased by s/s process. A qualitatively similar leaching behavior for SO4(2-), even for radically different wastes such as oily sludge and ash, solidified with two different types of cement was observed.     

TCLP underestimates leaching of arsenic from solid residuals under landfill conditions

Recent revision of the arsenic in drinking water standard will cause many utilities to implement removal technologies. Most of the affected utilities are expected to use adsorption onto solid media for arsenic removal. The arsenic-bearing solid residuals (ABSR) from adsorption processes are to be disposed of in nonhazardous landfills. The Toxicity Characteristic Leaching Procedure (TCLP) tests whether a waste is hazardous or nonhazardous; most solid residuals pass the TCLP. However, the TCLP poorly simulates the alkaline pH, low redox potential, biological activity, long retention time, and organic composition of mature landfills. These same conditions are likely to favor mobilization of arsenic from metal oxide sorbents. This study quantifies leaching of arsenic from Activated Alumina (AA) and Granular Ferric Hydroxide (GFH), two sorbents expected to be widely used for arsenic removal. The sorbents were subjected to the TCLP, the Waste Extraction Test (WET), an actual landfill leachate, and two synthetic leachate solutions. Up to tenfold greater arsenic concentration is extracted by an actual landfill leachate than by the TCLP. Equilibrium leachate concentrations are not achieved within 18 h (the TCLP duration) and an N2 headspace and end-over-end tumbling increase the rate of arsenic mobilization. However, tests with actual landfill leachate indicate the WET may also underestimate arsenic mobilization in landfills.     

Leaching assessments of hazardous materials in cellular telephones

Protocols for assessing the risks of discarded electronic products (e-waste) vary across jurisdictions, complicating the tasks of manufacturers and regulators. We compared the Federal Toxicity Characteristic Leaching Procedure (TCLP), California's Waste Extraction Test (WET), and the Total Threshold Limit Concentration (TTLC) on 34 phones to evaluate the consistency of hazardous waste classification. Our sample exceeded TCLP criteria only for lead (average 87.4 mg L(-1); range = 38.2-147.0 mg L(-1); regulatory limit = 5.0 mg L(-1), but failed TTLC for five metals: copper (average 203 g kg(-1); range = 186-224 g kg(-1); limit = 2.50 g kg(-1), nickel (9.25 g kg(-1); range = 6.34-11.20 g kg(-1); limit = 2.00 g kg(-1)), lead (10.14 g kg(-1); range = 8.2211.60 g kg(-1); limit = 1.00 g kg-1), antimony (1.02 g kg(-1); range = 0.86-1.29 g kg(-1); limit = 0.50 g kg(-1)), and zinc (11.01 g kg(-1); range = 8.82-12.80 g kg(-1); limit = 5.00 g kg(-1). Thresholds were not exceeded for WET. We detected several organic compounds, but at concentrations below standards. Brominated flame retardants were absent. These results improve existing environmental databases for e-waste and highlight the need to review regulatory testing for hazardous waste.     

Arsenic in groundwater in eastern New England: occurrence,controls, and human health implications

In eastern New England, high concentrations (greater than 10 microg/L) of arsenic occur in groundwater. Privately supplied drinking water from bedrock aquifers often has arsenic concentrations at levels of concern to human health, whereas drinking water from unconsolidated aquifers is least affected by arsenic contamination. Water from wells in metasedimentary bedrock units, primarily in Maine and New Hampshire, has the highest arsenic concentrations-nearly 30% of wells in these aquifers produce water with arsenic concentrations greater than 10 microg/L. Arsenic was also found at concentrations of 3-40 mg/kg in whole rock samples in these formations, suggesting a possible geologic source. Arsenic is most common in groundwater with high pH. High pH is related to groundwater age and possibly the presence of calcite in bedrock. Ion exchange in areas formerly inundated by seawater also may increase pH. Wells sampled twice during periods of 1-10 months have similar arsenic concentrations (slope = 0.89; r-squared = 0.97). On the basis of water-use information for the aquifers studied, about 103,000 people with private wells could have water supplies with arsenic at levels of concern (greater than 10 microg/L) for human health.     

Facilitated transport of diuron and glyphosate in high copper vineyard soils

The fate of organic herbicides applied to agricultural fields may be affected by other soil amendments, such as copper applied as a fungicide. The effect of copper on the leaching of diuron and glyphosate through a granitic and a calcareous soil was studied in the laboratory using sieved-soil columns. Each soil was enriched with copper sulfate to obtain soil copper concentrations of 125, 250, 500, and 1000 mg kg(-1). Glyphosate leaching was influenced by soil pH and copper concentration, whereas diuron leaching was not. In the calcareous soil, glyphosate leaching decreased as copper levels increased from 17 mg kg(-1) (background) to 500 mg kg(-1). In the granitic soil, glyphosate leaching increased as copper levels increased from 34 mg kg(-1) (background) to 500 mg kg(-1). The shapes of the copper elution curves in presence of glyphosate were similar to shapes of the glyphosate curves, suggesting the formation of Cu-glyphosate complexes that leach through the soil. Soil copper concentration does not influence diuron leaching. In contrast, increasing copper concentrations reduces glyphosate leaching through calcareous soils, and conversely, increases glyphosate leaching through granitic soils. Our findings suggest that the risk of groundwater contamination by glyphosate increases in granitic soils with elevated copper concentrations.     

Can arsenic occurrence rates in bedrock aquifers be predicted?

A high percentage (31%) of groundwater samples from bedrock aquifers in the greater Augusta area, Maine was found to contain greater than 10 μg L(-1) of arsenic. Elevated arsenic concentrations are associated with bedrock geology, and more frequently observed in samples with high pH, low dissolved oxygen, and low nitrate. These associations were quantitatively compared by statistical analysis. Stepwise logistic regression models using bedrock geology and/or water chemistry parameters are developed and tested with external data sets to explore the feasibility of predicting groundwater arsenic occurrence rates (the percentages of arsenic concentrations higher than 10 μg L(-1)) in bedrock aquifers. Despite the under-prediction of high arsenic occurrence rates, models including groundwater geochemistry parameters predict arsenic occurrence rates better than those with bedrock geology only. Such simple models with very few parameters can be applied to obtain a preliminary arsenic risk assessment in bedrock aquifers at local to intermediate scales at other localities with similar geology.     

Characterizing and quantilying controls on arsenic solubility over a pH range of 1-11 in a uranium mill-scale experiment

A mill-scale hydrometallurgical experiment (2700 m3 of effluent treated/day) was conducted for three months at the Rabbit Lake uranium mine site located in northern Saskatchewan, Canada, to determine the controls on the solubility of dissolved arsenic over a pH range of 1-11 and to develop a thermodynamic database for the dominant mineralogical controls on arsenic in the mill and the resulting mill tailings. The arsenic concentrations in the mill ranged from 526 mg/L at pH 1.0 (initial) to 1.34 mg/L at pH 10.8 (final discharge). Geochemical modeling of the chemistry data shows that arsenic solubility is controlled by the formation of scorodite (FeAsO4-2H2O) from pH 2.4 to pH 3.1, with 99.8% of dissolved arsenic precipitated as scorodite. Model results show that scorodite is unstable (releasing arsenic back in to solution) above pH 3.1 and arsenic adsorption to the surface of 2-line ferrihydrite is the dominant controlling factor in the solubility of arsenic from pH 3.2 to pH 11.0, with 99.8% of dissolved arsenic removed from solution via this mechanism. Finally, model results show -0.2% of the total dissolved arsenic adsorbs to the surface of amorphous aluminum hydroxide from pH 5.0 to pH 8.0. Minor alterations to the thermodynamic properties of arsenite and arsenate adsorption to 2-line ferrihydrite allowed the fit between measured mill-scale and modeled concentrations for the pH range of 3.2-11.0 to be optimized.     

Anion leaching from refinery oily sludge and ash from incineration of oily sludge stabilized/solidified with cement. Part II. Modeling

This paper presents the modeling of anion leaching (SO4(2-) and CrO4(2-)) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, 142.5 and 1142.5. Anion leaching was examined using a sequential toxicity characteristic leaching procedure (TCLP) test. To elucidate the mechanisms of sulfate and chromate leaching, we employed Visual MINTEQ, incorporating a multiple-problem setup. Specifically, 10-14 different problems, depending on the pH range of the leachates, were connected together in the same run. Each problem corresponded to one pH value of the leachate and the model run covered the pH range of the five sequential TCLP extractions. This modeling approach was tested using chemical equilibrium with or without sorption onto ferrihydrite. Good agreement between experimental and modeling results was obtained for sulfate leaching from solidified oily sludge and ash, considering surface complexation onto ferrihydrite on top of chemical equilibrium controlled by gypsum at pH <11 and ettringite at pH >11. Chromate leaching was described by chemical equilibrium, controlled by CaCrO4(s) (at pH <11) and Cr(VI)ettringite (at pH >11).     

Laboratory investigations of enhanced sulfate reduction as a groundwater arsenic remediation strategy

Landfills have the potential to mobilize arsenic via induction of reducing conditions in groundwater and subsequent desorption from or dissolution of arsenic-bearing iron phases. Laboratory incubation experiments were conducted with materials from a landfill where such processes are occurring. These experiments explored the potential for induced sulfate reduction to immobilize dissolved arsenic in situ. The native microbial community at this site reduced sulfate in the presence of added acetate. Acetate respiration and sulfate reduction were observed concurrent with dissolved iron concentrations initially increasing from 0.6 microM (0.03 mg L(-1)) to a maximum of 111 microM (6.1 mg L(-1)) and subsequently decreasing to 0.74 microM (0.04 mg L(-1)). Dissolved arsenic concentrations initially covaried with iron but subsequently increased again as sulfide accumulated, consistent with the formation of soluble thioarsenite complexes. Dissolved arsenic concentrations subsequently decreased again from a maximum of 2 microM (148 microg L(-1)) to 0.3 microM (22 microg L(-1)), consistent with formation of sulfide mineral phases or increased arsenic sorption at higher pH values. Disequilibrium processes may also explain this second arsenic peak. The maximum iron and arsenic concentrations observed in the lab represent conditions most equivalent to the in situ conditions. These findings indicate that enhanced sulfate reduction merits further study as a potential in situ groundwater arsenic remediation strategy at landfills and other sites with elevated arsenic in reducing groundwater.     

Removal of arsenic from synthetic acid mine drainage by electrochemical pH adjustment and coprecipitation with iron hydroxide

Acid mine drainage (AMD), which is caused by the biological oxidation of sulfidic materials, frequently contains arsenic in the form of arsenite, As(III), and/or arsenate, As(V), along with much higher concentrations of dissolved iron. The present work is directed toward the removal of arsenic from synthetic AMD by raising the pH of the solution by electrochemical reduction of H+ to elemental hydrogen and coprecipitation of arsenic with iron(III) hydroxide, following aeration of the catholyte. Electrolysis was carried out at constant current using two-compartment cells separated with a cation exchange membrane. Four different AMD model systems were studied: Fe(III)/As(V), Fe(III)/As(III), Fe(II)/As(V), and Fe(II)/As(III) with the initial concentrations for Fe(III) 260 mg/L, Fe(II) 300 mg/L, As(V), and As(III) 8 mg/L. Essentially quantitative removal of arsenic and iron was achieved in all four systems, and the results were independent of whether the pH was adjusted electrochemically or by the addition of NaOH. Current efficiencies were approximately 85% when the pH of the effluent was 4-7. Residual concentrations of arsenic were close to the drinking water standard proposed by the World Health Organization (10 microg/L), far below the mine waste effluent standard (500 microg/L).     

XAS study of arsenic coordination in Euglena gracilis exposed to arsenite

Among the few eukaryotes adapted to the extreme conditions prevailing in acid mine drainage, Euglenae are ubiquitous in these metal(loid)-impacted environments, where they can be exposed to As(III) concentrations up to a few hundreds of mg x L(-1). In order to evaluate their resistance to this toxic metalloid and to identify associated detoxification mechanisms, we investigated arsenic coordination in the model photosynthetic protozoan, Euglena gracilis, cultured at pH 3.2 and exposed to As(III) at concentrations ranging from 10 to 500 mg x L(-1). E. gracilis is shown to tolerate As(III) concentrations up to 200 mg * L(-1), without accumulating this metalloid. X-ray absorption spectroscopy at the As K-edge shows that, in the cells, arsenic mainly binds to sulfur ligands, likely in the form of arsenic-trisglutathione (As-(GS)3) or arsenic-phytochelatin (As-PC) complexes, and to a much lesser extent to carbon ligands, presumably in the form of methylated As(III)-compounds. The key role of the glutathione pathway in As(III) detoxification is confirmed by the lower growth rate of E. gracilis cultures exposed to arsenic, in the presence of buthionine sulfoximine, an inhibitor of glutathione synthesis. This study provides the first investigation at the molecular scale of intracellular arsenic speciation in E. gracilis and thus contributes to the understanding of arsenic detoxification mechanisms in a eukaryotic microorganism under extreme acid mine drainage conditions.     

Quality and safety assessment of ginseng extracts by determination of the contents of pesticides and metals.

Ginseng extracts are available as ingredients for improving energy and vitality and can be used in functional foods and as flavouring ingredients. A survey was been performed to determine the content of pesticides and toxic metals in ginseng extracts. Forty-seven samples from 20 suppliers, including both Panax ginseng C. A. Meyer (Asian ginseng) and P. quinquefolius (American ginseng) species, were analysed for arsenic content and for the following metals: aluminium, molybdenum, chromium, copper, magnesium, zinc, cadmium, mercury and lead, while pesticide residues were analysed in 30 samples from 17 suppliers. The results showed that 24 samples (80%) contained pesticides above the detection limit and 13 samples (43%) did not comply with the maximum residue limits (MRL) for total quintozene, hexachlorobenzene, total hexachlorocyclohexane, lindane, total heptachlor, e-chlorpyrifos and folpet, imposed for botanical extracts. Total quintozene, hexachlorobenzene, total hexachlorocyclohexane and lindane were present in all contaminated samples and exceeded the MRL in eleven samples, with levels up to 55 and 30 times their respective MRL. Cadmium (<0.05-259 microg kg(-1)), mercury (<0.3-72 microg kg(-1)), lead (3-2710 microg kg(-1)) and arsenic (<0.3-918 microg kg(-1)) were present in most samples at concentrations lower than the MRL imposed for flavouring substances. Among the other elements, aluminium (0.3-1068 mg kg(-1)) was the most abundant.