Sixty years of research on bracken fern (Pteridium spp.) toxins: Environmental exposure, health risks and recommendations for bracken fern control.

Bracken fern (Pteridium spp.) is a highly problematic plant worldwide due to its toxicity in combination with invasive properties on former farmland, in deforested areas and on disturbed natural habitats. The carcinogenic potential of bracken ferns has caused scientific and public concern for six decades. Its genotoxic effects are linked to illudane-type glycosides (ITGs), their aglycons and derivatives. Ptaquiloside is considered the dominating ITG, but with significant contributions from other ITGs. The present review aims to compile evidence regarding environmental pollution by bracken fern ITGs, in the context of their human and animal health implications. The ITG content in bracken fern exhibits substantial spatial, temporal, and chemotaxonomic variation. Consumption of bracken fern as food is linked to human gastric cancer but also causes urinary bladder cancers in bovines browsing on bracken. Genotoxic metabolites are found in milk and meat from bracken fed animals. ITG exposure may also take place via contaminated water with recent data pointing to concentrations at microgram/L-level following rain events. Airborne ITG-exposure from spores and dust has also been documented. ITGs may synergize with major biological and environmental carcinogens like papillomaviruses and Helicobacter pylori to induce cancer, revealing novel instances of chemical and biological co-carcinogenesis. Thus, the emerging landscape from six decades of bracken research points towards a global environmental problem with increasingly complex health implications.

Occurrence and stability of ptesculentoside, caudatoside and ptaquiloside in surface waters.

The illudane glycosides ptesculentoside (PTE), caudatoside (CAU) and ptaquiloside (PTA) are found in bracken ferns (Pteridium sp.). PTA is known to contaminate water bodies adjacent to bracken ferns and hence contribute to water toxicity. This study for the first time reports the presence of PTE and CAU in surface waters with concentrations up to 5.3 µg L-1 and outlines their stability under semi-natural conditions using water of two diverse lakes at their natural pH or pH adjusted to 6.5, with temperature controlled at 5 or 15 °C, and in the presence or absence of microbial activity. Under the same set of tested conditions the three illudane glycosides degraded at similar rates: with half-lives of approximately two days at pH 7.4 and 15 °C, and approximately 12 days at pH 5.2-6.5 and 5 °C. The water origin had significant influence on the degradation rates, but only due to its difference in pH. In most cases, the degradation rates of all the three illudane glycosides could be predicted using the existing first-order model for PTA hydrolysis. As PTE and CAU exhibit the same leaching pattern and stability as PTA, previous predictions of bracken environmental impact are likely underestimated, as PTE and CAU have not been monitored and included in the risk assessment.

Removal of phytotoxins in filter sand used for drinking water treatment.

Phytotoxins - toxins produced by plants - are contaminants with the potential to impair drinking water quality. They encompass a large group of toxic, partially persistent compounds that have been detected in seepage waters and in shallow wells used for drinking water production. If phytotoxins enter wells used for drinking water production, it is essential to know if the drinking water treatment processes will remove them from the water phase. However, it is currently unknown whether phytotoxins remain stable during traditional groundwater treatment using sand filters as the main treatment process. The objective of this study is to investigate removal potential of phytotoxins in biological sand filters and to asses if the removal potential is similar at different waterworks. Microcosms were set up with filter sand and drinking water collected at different groundwater-based waterworks. To be able to monitor phytotoxin removal ptaquiloside, caudatoside, gramine, sparteine, jacobine N-oxide, senecionine N-oxide and caffeine were applied at initial concentrations of 300 µg L-1, which is approx. two orders of magnitude higher than currently detected in environment, but expected to cover extreme environmental conditions. Removal was monitored over a period of 14 days. Despite the high initial concentration, all filter sands removed ptaquiloside and caudatoside completely from the water phase and at waterworks where pellet softening was implemented (pH 8.4) prior to rapid sand filtration, complete removal occurred within the first 30 min. All filter sands removed gramine and sparteine, primarily by a biological process, while jacobine N-oxide, senecionine N-oxide and caffeine were recalcitrant in the filter sands. During degradation of ptaquiloside and caudatoside we observed formation and subsequent removal of degradation products pterosin B and A. Filter sands with the highest removal potential were characterised by high contents of deposited iron and manganese oxides and hence large specific surface areas. Difference between bacterial communities investigated by 16S rRNA gene analyses did not explain different removal in the filter sands. All five investigated filter sands showed similar degradation patterns regardless of water chemistry and waterworks of origin. In drinking water treatment systems biological sand filters might therefore remove phytotoxin contaminants such as ptaquiloside, caudatoside, gramine, sparteine, while for other compounds e.g. jacobine N-oxide, senecionine N-oxide further investigations involving more advanced treatment options are needed.

Presence of the carcinogen ptaquiloside in fern-based food products and traditional medicine: Four cases of human exposure.

Ptaquiloside (PTA) is a natural carcinogen present in many ferns. Brackens (Pteridium sp.) contain PTA and are classified by WHO/IARC as ' … possibly carcinogenic to humans', however, these ferns are used in food, traditional medicine and as food supplements around the world. This study aimed to outline the presence of PTA in different human exposure routes by using and validating an LC-MS based protocol to test the contents of PTA in commercial products, the degradation product Pterosin B (PtB) and wild specimens from Europe, Asia and North America. The Limit of Detection of the protocol was 0.024 µg g-1 for PTA and 0.028 µg g-1 for PtB. PTA and PtB were present in most wild specimens (PTA: BD - 6300 ± 520 µg g-1; PtB: BD - 449 ± 1 µg g-1) while commercial products made from fronds, as well as fronds prepared as traditional Chinese medicine, were in the range 44 ± 3 to 666 ± 33 µg g-1 for PTA and BD to 1653 ± 184 µg g-1 for PtB. This study did not find PTA/PtB in rhizomes and products made thereof nor in homoeopathic products based on bracken. Boiling or drying bracken showed to reduce PTA some degree but cannot remove it completely. Interestingly, crosiers with no PTA/PtB were found in the USA, indicating a potential for commercial production of PTA-free fronds.

The invasive butterbur contaminates stream and seepage water in groundwater wells with toxic pyrrolizidine alkaloids.

Pyrrolizidine alkaloids (PAs) are persistent mutagenic and carcinogenic compounds produced by many common plant species. Health authorities recommend minimising human exposure via food and medicinal products to ensure consumer health and safety. However, there is little awareness that PAs can contaminate water resources. Therefore, no regulations exist to limit PAs in drinking water. This study measured a PA base concentration of ~ 70 ng/L in stream water adjacent to an invasive PA-producing plant Petasites hybridus (Asteraceae). After intense rain the PA concentration increased tenfold. In addition, PAs measured up to 230 ng/L in seepage water from groundwater wells. The dominant PAs in both water types corresponded to the most abundant PAs in the plants (senkirkine, senecionine, senecionine N-oxide). The study presents the first discovery of persistent plant toxins in well water and their associated risks. In addition, it for the first time reports monocrotaline and monocrotaline N-oxide in Petasites sp.

Hemorrhagic diathesis in cattle due to consumption of Adiantopsis chlorophylla (Swartz) Fée (Pteridaceae).

An outbreak of acute febrile syndrome associated with coagulopathy and severe pancytopenia occurred in cattle grazing in paddocks with high infestation by Adiantopsis chlorophylla. The administration of the plant to a calf reproduced the same signs and lesions seen in spontaneous cases. Similar syndromes are caused by ptaquiloside from bracken fern. Traces of the ptaquiloside-like molecule caudatoside were detected together with 0.03-0.24 mg/g of it's degradation product pterosin A, in dry fronds of the plant. In conclusion, A. chlorophylla is a cause of hemorrhagic diathesis in cattle.

A rapid GC-FID method for determination of sabinene, ß-pinene, α-thujone and ß-thujone in the essential oil of Kitchen Sage (Salvia officinalis L.).

Terpenes and terpenoids are dominant fragrances in the essential oils of many economically important fruits and vegetables. Hence, content and variation are important factors in the evaluation and common perception of food quality. Sabinene, ß-pinene, α-thujone and ß-thujone are examples of such compounds found in the different species of Sage. Sabinene and ß-pinene are spicy compounds much used by the fragrance industry while the two thujones are highly toxic. Here, we report a rapid method for quantification of these compounds in the essential oil of Sage. The total analytical time is approx. 7,5 min in contrast to approx. 30 min for similar gas chromatographic methods. The analytical method had a linear range of 28-342 mg L-1 for the different compounds, with an analytical precision of 0,6-0,9% for standards. Correlation coefficients were 0,9993-1,0000. The Limit of Detection of all compounds were 0,02-0,9 mg L-1 and the Limit of Quantification were 0,08-3,0 mg L-1. The technique was used for quantification of the compounds in seven commercial essential Sage oils and in a pilot study of the effect of ozone on the terpenes and terpenoids in fresh Sage leaves. Large variation was observed between the different commercial samples, of which some were thujone dominant and some did not have any content of thujone at all. Treatment of fresh Sage leaves with ozone caused degradation of the terpenes sabinene and ß-pinene whereas the terpenoids α/ß-thujone were more resistant to degradation.

Fast LC-MS quantification of ptesculentoside, caudatoside, ptaquiloside and corresponding pterosins in bracken ferns.

Ptaquiloside (PTA) is an illudane glycoside partly responsible for the carcinogenicity of bracken ferns (Pteridium sp.). The PTA analogues ptesculentoside (PTE) and caudatoside (CAU) have similar biochemical reactivity. However, both compounds are highly under-investigated due to the lack of analytical standards and appropriate methods. This study presents a robust method for preparation of analytical standards of PTE, CAU, PTA, the corresponding hydrolysis products: pterosins G, A and B, and an LC-MS based method for simultaneous quantification of the six compounds in bracken. The chromatographic separation of analytes takes 5 min. The observed linear range of quantification was 20-500 µg/L for PTA and pterosin B, and 10-250 µg/L for the remaining compounds (r > 0.999). The limits of detection were 0.08-0.26 µg/L for PTE, CAU and PTA and 0.01-0.03 µg/L for the pterosins, equivalent to 2.0-6.5 µg/g and 0.25-0.75 µg/g in dry weight, respectively. The method was applied on 18 samples of dried fern leaves from 6 continents. Results demonstrated high variation in concentrations of PTE, CAU and PTA with levels prior to hydrolysis up to 3,900, 2,200 and 2,100 µg/g respectively. This is the first analytical method for simultaneous and direct measurement of all six compounds. Its application demonstrated that bracken ferns contain significant amounts of PTE and CAU relative to PTA.

Fate of ptaquiloside-A bracken fern toxin-In cattle.

Ptaquiloside is a natural toxin present in bracken ferns (Pteridium sp.). Cattle ingesting bracken may develop bladder tumours and excrete genotoxins in meat and milk. However, the fate of ptaquiloside in cattle and the link between ptaquiloside and cattle carcinogenesis is unresolved. Here, we present the toxicokinetic profile of ptaquiloside in plasma and urine after intravenous administration of ptaquiloside and after oral administration of bracken. Administered intravenously ptaquiloside, revealed a volume of distribution of 1.3 L kg-1 with a mean residence-time of 4 hours. A large fraction of ptaquiloside was converted to non-toxic pterosin B in the blood stream. Both ptaquiloside and pterosin B were excreted in urine (up to 41% of the dose). Oral administration of ptaquiloside via bracken extract or dried ferns did not result in observations of ptaquiloside in body fluids, indicating deglycosolidation in the rumen. Pterosin B was detected in both plasma and urine after oral administration. Hence, transport of carcinogenic ptaquiloside metabolites over the rumen membrane is indicated. Pterosin B recovered from urine counted for 7% of the dose given intravenously. Heifers exposed to bracken for 7 days (2 mg ptaquiloside kg-1) developed preneoplastic lesions in the urinary bladder most likely caused by genotoxic ptaquiloside metabolites.

A novel technique for determination of the fructose, glucose and sucrose distribution in nectar from orchids by HPLC-ELSD.

The dominant components in floral nectar is fructose, glucose and sucrose. The concentration and the ratio between the sugars are indicative for plant species and play an important part in the interplay between plants and pollinators. In this paper we present a novel HPLC-ELSD based analytical method for sugar characterization of nectar from orchids. Nectar was collected on Whatman No. 1 paper and preserved in the field by 70 v/v% ethanol. The analytical method had a linear range up to at least 3000 mg L-1 for all 3 sugars with a precision of 1.5-1.7%. Correlation coefficients were 0.9999 to 1.0000. The LOD of all sugars were 5-7 mg L-1 and the LOQ were 17-19 mg L-1. Field samples were stable for min. 7 weeks at -18 °C. The technique was applied to two species of Platanthera (Orchidaceae) in order to test whether species-related differences in sugar composition could be observed. No differences were found between the two species, which were sucrose-dominant (53.5-100%) though with high variation within species and between individual flowers.

Screening for Ptaquiloside in Ferns: Using Herbarium Specimens for Qualitative Mapping Purposes.

INTRODUCTION: Ptaquiloside (PTA) is a noxious carcinogen found widespread in Bracken (Pteridium sp.) but with scattered and unresolved distribution outside the genus. The carcinogen causes Bovine Enzootic Haematuria among cattle all-over the World and is under suspicion of causing human cancers. OBJECTIVE: To set-up a methodology for large-scale qualitative studies on the distribution of PTA in ferns using already available herbarium specimens as source. METHODOLOGY: PTA and the main degradation product pterosin B (PtB) were quantified in aqueous frond extracts by HPLC-DAD. PTA was quantified after forced reaction into PtB. Optimal reaction conditions were tested using hydrochloric acid, sulphuric acid, trifluoroacetic acid (TFA), acetic acid and temperature as the experimental variables. A pair-wise test for PTA degradation in plant-press were used to explore the effect of this preservation regime. A selection of up to 50 years old Bracken herbarium specimens were tested for PTA and PtB. The methodology was applied on 21 fern species from Denmark. RESULTS: An optimised TFA-based method results in 30.7% higher conversion and a 1:1 reaction between PTA and PtB. Full three-dimensional resolution of the analyte was obtained. Preservation of fronds in a plant press increase formation of PtB. Hence, the method is only suitable for qualitative studies. Presence of PTA and PtB were found in samples up to 50 years old. Among 21 ferns tested, the compounds were only found in Pteridium aquilinum. CONCLUSION: Herbarium specimens up to 50 years old can be used for explorative risk assessment of ferns using HPLC-DAD for quantification and identification. Copyright © 2017 John Wiley & Sons, Ltd.

Dissipation of pterosin B in acid soils - Tracking the fate of the bracken fern carcinogen ptaquiloside.

Bracken ferns (Pteridium spp.) are well-known for their carcinogenic properties, which are ascribed to the content of ptaquiloside and ptaquiloside-like substances. Ptaquiloside leach from the ferns and may cause contamination of drinking water. Pterosin B is formed by hydrolysis of ptaquiloside. In soil, Pterosin B is adsorbed more strongly and it is expected to have a slower turnover than ptaquiloside. We thus hypothesized that pterosin B may serve as an indicator for any past presence of ptaquiloside. Pterosin B degradation was studied in acid forest soils from bracken-covered and bracken-free areas. Soil samples were incubated with pterosin B at 3 and 8 µg g-1 for 10 days, whereas sterile (autoclaved) samples were incubated for 23 days. Pterosin B showed unexpected fast degradation in soils with full degradation in topsoils in 2-5 days. Pterosin B dissipation followed the sum of two-first order reactions. The initial fast reaction with half-lives of 0.7-3.5 h contributed 11-59% of the total pterosin B degradation, while the slow reaction was 20-100 times slower than the fast reaction. Total dissipation half-lives were shorter for loamy sand (4 h) than for sandy loam soils (28 h). No degradation of pterosin B took place under sterile conditions assuming observed dissipation during the first 3 h could be attributed to irreversible sorption. Our results demonstrate that pterosin B is microbially degraded and that pterosin B is as unstable as ptaquiloside and hence cannot be used as an indicator for former presence of ptaquiloside in soil.

Land management of bracken needs to account for bracken carcinogens--a case study from Britain.

Bracken ferns are some of the most widespread ferns in the World causing immense problems for land managers, foresters and rangers. Bracken is suspected of causing cancer in Humans due to its content of the carcinogen ptaquiloside. Ingestion of bracken, or food and drinking water contaminated with ptaquiloside may be the cause. The aim of this study was to monitor the content of ptaquiloside in 20 bracken stands from Britain to obtain a better understanding of the ptaquiloside dynamics and to evaluate the environmental implications of using different cutting regimes in bracken management. The ptaquiloside content in fronds ranged between 50 and 5790 µg/g corresponding to a ptaquiloside load in the standing biomass of up to 590 mg/m(2) in mature fronds. Ptaquiloside was also found in the underground rhizome system (11-657 µg/g) and in decaying litter (0.1-5.8 µg/g). The amount of ptaquiloside present in bracken stands at any given time is difficult to predict and did not show any correlations with edaphic growth factors. The content of ptaquiloside turned out to be higher in fronds emerging after cutting compared to uncut fronds. Environmental risk assessment and bracken management must therefore be based on actual and site specific determinations of the ptaquiloside content. Care must be taken to avoid leaching from cut ferns to aquifers and other recipients and appropriate precautionary measures must be taken to protect staff from exposure to bracken dust.

Determination of ptaquiloside and pterosin B derived from bracken (Pteridium aquilinum) in cattle plasma, urine and milk.

Ptaquiloside (PTA) is a toxin from bracken fern (Pteridium sp.) with genotoxic effects. Hydrolysis of PTA leads to the non-toxic and aromatised indanone, pterosin B (PTB). Here we present a sensitive, fast, simple and direct method, using SPE cartridges to clean and pre-concentrate PTA and PTB in plasma, urine and milk followed by LC-MS quantification. The average recovery of PTA in plasma, urine, and milk was 71, 88 and 77%, respectively, whereas recovery of PTB was 75, 82 and 63%. The method LOQ for PTA and PTB in plasma was 1.2 and 3.7ngmL(-1), 52 and 33ngmL(-1) for undiluted urine and 5.8 and 5.3ngmL(-1) for milk. The method is repeatable within and between days, with RSD values lower than 15% (PTA) and 20% (PTB). When PTA and PTB spiked samples were stored at -18°C for 14 days both compounds remained stable. In contrast, the PTA concentration was reduced by 15% when PTA spiked plasma was left for 5h at room temperature before SPE clean-up, whereas PTB remained stable. The method is the first to allow simultaneous quantification of PTA and PTB in biological fluids in a relevant concentration range. After intravenous administration of 0.092mg PTA per kgbw in a heifer, the plasma concentration was more than 300ngmL(-1) PTA and declined to 9.8ngmL(-1) after 6h, PTB was determined after 10min at 50ngmL(-1.)

Ptaquiloside in bracken spores from Britain.

Secondary metabolites from bracken fern (Pteridium aquilinum (L.) Kuhn) are suspected of causing cancer in humans. The main carcinogen is the highly water-soluble norsesquiterpene glucoside ptaquiloside, which may be ingested by humans through food, e.g. via contaminated water, meat or milk. It has been postulated that carcinogens could also be ingested through breathing air containing bracken spores. Ptaquiloside has not previously been identified in bracken spores. The aim of the study was to determine whether ptaquiloside is present in bracken spores, and if so, to estimate its content in a collection of spores from Britain. Ptaquiloside was present in all samples, with a maximum of 29 µg g(-1), which is very low compared to other parts of the fern. Considering the low abundance of spores in breathing air under normal conditions, this exposure route is likely to be secondary to milk or drinking water.

Degradation kinetics of ptaquiloside in soil and soil solution.

Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glycoside produced in bracken (Pteridium aquilinum (L.) Kuhn), a widespread, aggressive weed. Transfer of PTA to soil and soil solution eventually may contaminate groundwater and surface water. Degradation rates of PTA were quantified in soil and soil solutions in sandy and clayey soils subjected to high natural PTA loads from bracken stands. Degradation kinetics in moist soil could be fitted with the sum of a fast and a slow first-order reaction; the fast reaction contributed 20 to 50% of the total degradation of PTA. The fast reaction was similar in all horizons, with the rate constant k(1F) ranging between 0.23 and 1.5/h. The slow degradation, with the rate constant k(1S) ranging between 0.00067 and 0.029/ h, was more than twice as fast in topsoils compared to subsoils, which is attributable to higher microbial activity in topsoils. Experiments with sterile controls confirmed that nonmicrobial degradation processes constituted more than 90% of the fast degradation and 50% of the slow degradation. The lower nonmicrobial degradation rate observed in the clayey compared with the sandy soil is attributed to a stabilizing effect of PTA by clay silicates. Ptaquiloside appeared to be stable in all soil solutions, in which no degradation was observed within a period of 28 d, in strong contrast to previous studies of hydrolysis rates in artificial aqueous electrolytes. The present study predicts that the risk of PTA leaching is controlled mainly by the residence time of pore water in soil, soil microbial activity, and content of organic matter and clay silicates.

Rate of hydrolysis and degradation of the cyanogenic glycoside - dhurrin - in soil.

Cyanogenic glycosides are common plant toxins. Toxic hydrogen cyanide originating from cyanogenic glycosides may affect soil processes and water quality. In this study, hydrolysis, degradation and sorption of dhurrin (4-hydroxymandelonitrile-beta-d-glucoside) produced by sorghum has been studied in order to assess its fate in soil. The log K(ow) of dhurrin was -1.18+/-0.08 (22 degrees C). Hydrolysis was a first-order reaction with respect to dhurrin and hydroxyl ion concentrations. Half lives ranged from 1.2h (pH 8.6; 25 degrees C) to 530d (pH 4; 25 degrees C). The activation energy of hydrolysis was 112+9kJ. At pH 5.8 and room temperature, addition of humic acids (50gl(-1)) increased the rate of hydrolysis tenfold, while addition of kaolinite or goethite (100-250gl(-1)) both decreased the rate considerably. No significant sorption to soil components could be observed. The degradation rates of dhurrin in top and subsoils of Oxisols, Ultisols, Alfisols and Mollisols were studied at 22 degrees C (25mgl(-1), soil:liquid 1:1 (w:V), pH 3.8-8.1). Half-lives were 0.25-2h for topsoils, and 5-288h in subsoils. Hydrolysis in solution explained up to 45% of the degradation in subsoils whereas the contribution in topsoils was less than 14%, indicating the importance of enzymatic degradation processes. The highest risk of dhurrin leaching will take place when the soil is a low activity acid shallow soil with low content of clay minerals, iron oxides and humic acids.

Genotoxic activity and inhibition of soil respiration by ptaquiloside, a bracken fern carcinogen.

Ptaquiloside (PTA) is a natural toxin produced by bracken (Pteridium aquilinum [L.] Kuhn). Assessment of PTA toxicity is needed because PTA deposited from bracken to soil may leach to surface and groundwater. Inhibition of soil respiration and genotoxic activity of PTA was determined by a soil microbial carbon transformation test and an umu test, respectively. In the carbon transformation test, sandy loam soil was incubated at five different initial concentrations of PTA for a period of 28 d, after which glucose was added and respiration measured for 12 consecutive hours. The tests were performed at 20 degrees C and soil moisture content of approximately 15%. For soil material sampled in the autumn, initial PTA concentrations ranging from 0.008 to 40.6 microg PTA/g dry soil were tested. From fitting of data by a sigmoidal function, a 10% effect dose (ED10) was estimated to 13 microg PTA/ g dry soil, with an upper 95% confidence limit of 43 microg PTA/g dry soil and a 95% lower confidence limit of -infinity microg PTA/g dry soil. For soil material sampled in late winter, initial PTA concentrations ranging from 1.56 to 212 microg PTA/g dry soil were tested, resulting in an ED10 value of 55 microg PTA/g dry soil, with an upper 95% confidence limit of 70 microg PTA/g dry soil and a 95% lower confidence limit of 40 microg PTA/g dry soil. The genotoxic activity of PTA was determined using the umu test without and with metabolic activation (addition of S9 rat liver homogenate). In tests with addition of S9, the induction ratio exceeded the critical ratio of 1.5 at a PTA concentration of 46 +/- 16 microg/ml and, in tests without S9, the critical ratio was exceeded at a PTA concentration of 279 +/- 22 microg/ml. The genotoxicity of PTA is comparable to that of quercetin, another bracken constituent. The toxicity of PTA toward microorganisms prolongs the persistence of PTA in terrestrial environments, increasing the risk of PTA leaching to drainage and groundwater.

Sorption, degradation and mobility of ptaquiloside, a carcinogenic Bracken (Pteridium sp.) constituent, in the soil environment.

Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glucoside produced by Bracken in amounts up to at least 500 mg m(-2). The toxin is transferred from Bracken to the underlying soil from where it may leach to surface and groundwater's impairing the quality of drinking water. The objectives of the present study were to characterize the solubility, degradation and retention of PTA in soils in order to evaluate the risk for groundwater contamination. PTA was isolated from Bracken. The logarithmic octanol-water and ethyl acetate-water partitioning coefficients for PTA were -0.63 and -0.88, respectively, in agreement with the high water solubility of the compound. PTA hydrolysed rapidly in aqueous solution at pH 4 or lower, but was stable above pH 4. Incubation of PTA with 10 different soils at 25 degrees C showed three different first order degradation patterns: (i) rapid degradation observed for acid sandy soils with half life's ranging between 8 and 30 h decreasing with the soil content of organic matter, (ii) slow degradation in less acid sandy soils with half-lives of several days, and (iii) fast initial degradation with a concurrent solid phase-water partitioning reaction observed for non-acid, mostly clayey soils. The presence of clay silicates appears to retard the degradation of PTA, possibly through sorption. Degradation at 4 degrees C was generally of type (iii) and degradation rates were up to 800 times lower than at 25 degrees C. Sorption isotherms for the same set of soils were almost linear and generally showed very low sorption affinity with distribution coefficients in the range 0.01-0.22 l kg(-1) at a solution concentration of 1 mg l(-1) except for the most acid soil; Freundlich affinity coefficients increased linearly with clay and organic matter contents. Negligible sorption was also observed in column studies where PTA and a non-sorbing tracer showed almost coincident break-through. Leaching of PTA to the aqueous environment will be most extensive on sandy soils, having pH >4 and poor in organic matter which are exposed to high precipitation rates during cold seasons.

Distribution of the carcinogenic terpene ptaquiloside in bracken fronds, rhizomes (Pteridium aquilinum), and litter in Denmark.

The distribution of ptaquiloside (PTA) was studied in four Danish bracken populations in order to evaluate the transfer of PTA from ferns to soil. Populations showed statistically significant differences in PTA contents of fronds and rhizomes despite large in-site variations. The highest concentrations were encountered in fronds with concentrations ranging between 213 and 2145 microg/g, while rhizomes had concentrations between 11 and 902 microg/g. PTA was present in soil materials in amounts of 0.22-8.49 microg/g but apparently with no correlation with PTA contents of fronds or rhizomes. Laboratory tests showed that water could leach PTA from bracken fronds, which is in support of the high soil contents observed at sites exposed to heavy showers just before sampling. The observed soil contents correspond to estimated soil solution concentrations of 200-8500 microg/liter, demonstrating a substantial risk of PTA contamination of surface water and groundwater.