Gero Leson | University of Cologne (original) (raw)

Papers by Gero Leson

Journal of Industrial Hemp, 2003

In recent years, the presence of trace residual delta-9-tetrahydrocannabinol (THC) in food and co... more In recent years, the presence of trace residual delta-9-tetrahydrocannabinol (THC) in food and cosmetics from hemp seed and seed derivatives (oil, hulled seed) has raised concerns over THC's potentially adverse impacts on human health and on the results of workplace drug tests for marijuana. Two desktop studies and one experimental study were conducted to evaluate whether (1) the ingestion of

Journal of Analytical Toxicology, 2001

Foods containing seeds or oil of the hemp plant (Cannabis sativa t.) are increasingly found in re... more Foods containing seeds or oil of the hemp plant (Cannabis sativa t.) are increasingly found in retail stores in the U.S. The presence of Ag-tetrahydrocannabinol (THC) in these foods has raised concern over their impact on the results of workplace drug tests for marijuana. Previous studies have shown that eating hemp foods can cause screening and confirmed positive results in urine specimens. This study evaluated the impact of extended daily ingestion of THC via hemp oil on urine levels of its metaholite 11-nor-9-carboxy-A% tetrahydrocannabinol (THC-COOH) for four distinct daily THC doses. Doses were representative of THC levels now commonly found in hemp seed products and a range of conceivable daily consumption rates. Fifteen THC-na'ive adults ingested, over four successive 10-day periods, single daily THC doses ranging from 0.09 to 0.6 rag. Subjects self-administered THC in 15.mL aliquots (20 mL for the 0.6-rag dose) of four different blends of hemp and canola oils. Urine specimens were collected prior to the first ingestion of oil, on days 9 and 10 of each of the four study periods, and 1 and 3 days after the last ingestion. All specimens were screened for cannabinoids by radioimmunoassay (Immunalysis Direct RIA Kit), confirmed for THC-COOH by gas chromatography-mass spectrometry (GC-MS), and analyzed for creatinine to identify dilute specimens. None of the subjects who ingested daily doses of 0.45 mg of THC screened positive at the 50-ng/mL cutoff. At a daily THC dose of 0.6 rag, one specimen screened positive. The highest THC-COOH level found by GC-MS in any of the specimens was 5.2 ng/mL, well below the 15-ng/mL confirmation cutoff used in federal drug testing programs. A THC intake of 0.6 rag/day is equivalent to the consumption of * Author to whom correspondence should be addressed, approximately 125 mt of hemp oil containing 5 pg/g of THC or 300 g of hulled seeds at 2 pg/g. These THC concentrations are now typical in Canadian hemp seed products. Based on our findings, these concentrations appear to be sufficiently low to prevent confirmed positives from the extended and extensive consumption of hemp foods.

Addiction, 2007

Objective Development of a rational and enforceable basis for controlling the impact of cannabis ... more Objective Development of a rational and enforceable basis for controlling the impact of cannabis use on traffic safety. Methods An international working group of experts on issues related to drug use and traffic safety evaluated evidence from experimental and epidemiological research and discussed potential approaches to developing per se limits for cannabis. Results In analogy to alcohol, finite (non-zero) per se limits for delta-9-tetrahydrocannabinol (THC) in blood appear to be the most effective approach to separating drivers who are impaired by cannabis use from those who are no longer under the influence. Limited epidemiological studies indicate that serum concentrations of THC below 10 ng/ml are not associated with an elevated accident risk. A comparison of meta-analyses of experimental studies on the impairment of driving-relevant skills by alcohol or cannabis suggests that a THC concentration in the serum of 7-10 ng/ml is correlated with an impairment comparable to that caused by a blood alcohol concentration (BAC) of 0.05%. Thus, a suitable numerical limit for THC in serum may fall in that range. Conclusions This analysis offers an empirical basis for a per se limit for THC that allows identification of drivers impaired by cannabis. The limited epidemiological data render this limit preliminary.

Physical Review Letters, 1985

In the past, biofilters have primarily controlled dilute, usually odorous, off-gases with VOC con... more In the past, biofilters have primarily controlled dilute, usually odorous, off-gases with VOC concentrations < 1 g/m{sup 3} and VOC loads < 50 g/m{sup 3}h. Yet, US industry has also shown an interest in the removal of higher concentrations of VOC and hazardous air pollutants (HAP). In two such instances, the treatment of high loads of ethanol from a foundry and a bakery, respectively, caused degradation limitation, the formation of odorous acetic acid, and problems maintaining the proper moisture content because of the exothermic nature of the biodegradation process. For a more detailed study of the behavior of biofilters at high loads of binary VOC mixtures, two bench-scale biofilters were operated using a commercially available media and a mixture of wood chips and compost. Both were exposed to various high loads of mixtures of ethyl acetate and toluene. Concentration profiles and the corresponding elimination vs. load curves were established through frequent grab-sampling and GC analysis. Biofilter response to two frequently encountered operating problems, i.e. media dry-out and temperatures exceeding 40 C, was also evaluated under controlled conditions. Resident microbial populations were characterized to assure the presence of organisms capable of degrading both major off-gas constituents. The results demonstrated several characteristicsmore » of high-load biofilters: maximum elimination capacities for ethyl acetate were typically limited to 200 g/m3h; despite the presence of toluene degraders, the removal of toluene was inhibited by high loads of ethyl acetate; several by-products, particularly ethanol, were formed; and short-term dry-out and temperature excursions resulted in reduced performance. The paper discusses these observations in more detail. Its findings provide a quantitative assessment of some of the limitations of biofilters used for the treatment of high VOC loads.« less

Industrial Applications of Natural Fibres, 2010

... Valuable information on the production and uses of natural fibres in EC products was contribu... more ... Valuable information on the production and uses of natural fibres in EC products was contributed by Gordon de Silva, Serendipol (Pvt) Ltd, Kuliyapitiya, Sri Lanka, Bernd Frank, BaFa GmbH, Malsch ... Elmwood (2004) Comparative advantages of sisal, coir and jute geotextiles. ...

Journal of Agricultural and Food Chemistry, 2010

The macronutrient composition and the quality of protein of hemp seed and products derived from h... more The macronutrient composition and the quality of protein of hemp seed and products derived from hemp seed grown in Western Canada were determined. Thirty samples of hemp products (minimum 500 g), including whole hemp seed, hemp seed meal from cold-press expelling, dehulled, or shelled, hemp seed and hemp seed hulls, were obtained from commercial sources. Proximate analysis, including crude protein (% CP), crude fat (% fat) and fiber, as well as full amino acid profiles, were determined for all samples. Protein digestibility-corrected amino acid score (PDCAAS) measurements, using a rat bioassay for protein digestibility and the FAO/WHO amino acid requirement of children (2-5 years of age) as reference, were conducted on subsets of hemp products. Mean (±SD) percentage CP and fat were 24.0(2.1) and 30.4(2.7) for whole hemp seed, 40.7(8.8) and 10.2(2.1) for hemp seed meal, and 35.9(3.6) and 46.7(5.0) for dehulled hemp seed. The percentage protein digestibility and PDCAAS values were 84.1-86.2 and 49-53% for whole hemp seed, 90.8-97.5 and 46-51% for hemp seed meal, and 83.5-92.1 and 63-66% for dehulled hemp seed. Lysine was the first limiting amino acid in all products. Removal of the hull fraction improved protein digestibility and the resultant PDCAAS value. The current results provide reference data in support of protein claims for hemp seed products and provide evidence that hemp proteins have a PDCAAS equal to or greater than certain grains, nuts, and some pulses.

… by an expert panel. …, 2005

Executive Summary This report presents the findings, conclusions and recommendations of a panel o... more Executive Summary This report presents the findings, conclusions and recommendations of a panel of experts on the issue of driving under the influence of cannabis (DUIC) and on strategies for controlling its potential impact on traffic safety. The panel's primary objective ...

Journal of the Air & Waste Management Association, 1991

Biofiltration is a relatively recent air pollution control (APC) technology in which off-gases co... more Biofiltration is a relatively recent air pollution control (APC) technology in which off-gases containing biodegradable volatile organic compounds (VOC) or inorganic air toxics are vented through a biologically active material. This technology has been successfully applied in Germany and The Netherlands in many full-scale applications to control odors, VOC and air toxic emissions from a wide range of industrial and public sector sources. Control efficiencies of more than 90 percent have been achieved for many common air pollutants. Due to lower operating costs, biofiltration can provide significant economic advantages over other APC technologies if applied to off-gases that contain readily biodegradable pollutants in low concentrations. Environmental benefits include low energy requirements and the avoidance of cross media transfer of pollutants. This paper reviews the history and current status of biofiltration, outlines its underlying scientific and engineering principles, and discusses the applicability of biofilters for a wide range of specific emission sources.

Dillbohner's and Leson's pamphlet briefly alludes to the strangeness of what their collec... more Dillbohner's and Leson's pamphlet briefly alludes to the strangeness of what their collective composed of five European artists experienced in the United States, and the resulting installation.

Http Dx Doi Org 10 1080 10473289 1997 10464410, Dec 27, 2011

Journal of Environmental Engineering, Jun 1, 1997

Journal of the Air & Waste Management Association, 1999

To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with r... more To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with relatively low volatile organic compound (VOC) concentrations (<1 g m-3) and VOC loads (<50 g m-3 hr-1). Recently, however, U.S. industry has shown an interest in applying biofilters to higher concentrations of VOCs and hazardous air pollutants (HAPs). In this study, the behavior of biofilters under high loads of binary VOC mixtures was studied. Two benchscale biofilters were operated using a commercially available medium and a mixture of wood chips and compost. Both were exposed to varying mixtures of ethyl acetate and toluene. Concentration profiles and the corresponding removal efficiencies as a function of VOC loading were determined through frequent grab-sampling and GC analysis. Biofilter response to two frequently encountered operating problems-media dry-out and operating temperatures exceeding 40 °C-was also evaluated under controlled conditions. Microbial populations were IMPLICATIONS To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with relatively low VOC concentrations. Yet there is a growing interest in expanding to higher concentrations the range of suitable applications for biological waste air treatment. However, this type of application has a high rate of system failure. Impediments for this application were reported in two recent case studies in which the treatment of high loads of ethanol from a foundry and a bakery, respectively, resulted in reduced percentage removal of the contaminants, formation of odorous acetic acid, and problems maintaining the proper moisture content because of the exothermic nature of the biodegradation process. The present study reports bench-scale operation of biofilters under high VOC loading conditions of mixed pollutant and the factors that lead to these adverse operating states also monitored to confirm the presence of organisms capable of degrading both major off-gas constituents. The results demonstrated several characteristics of biofilters operating under high VOC load conditions. • Maximum elimination capacities for ethyl acetate were typically in the range of 200 g m-3 hr-1. • Despite the presence of toluene degraders, the removal of toluene was inhibited by high loads of ethyl acetate. • Several byproducts, particularly ethanol, were formed. • Short-term dry-out and temperature excursions resulted in reduced performance.