title: Re-evaluation of groundwater monitoring data for glyphosate and bentazone by taking detection limits into account.
abstract: Current regulatory assessment of pesticide contamination of Danish groundwater is exclusively based on samples with pesticide concentrations above detection limit. Here we demonstrate that a realistic quantification of pesticide contamination requires the inclusion of "non-detect" samples i.e. samples with concentrations below the detection limit, as left-censored observations. The median calculated pesticide concentrations are shown to be reduced 10(4) to 10(5) fold for two representative herbicides (glyphosate and bentazone) relative to the median concentrations based upon observations above detection limits alone.
authors.affiliation: Ålegårdsvej 29, 2740 Skovlunde, Denmark.
authors.forename: Claus Toni
authors.initials: CT
authors.lastname: Hansen
authors.affiliation: Nutrition, Exercise and Sports, University of Copenhagen, Rolighedsvej 26, 1958 Frederiksberg C, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Ritz
authors.affiliation: Mathematics and Statistics, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gerhard
authors.affiliation: SEGES P/S, Crops & Environment, Agro Food Park 15, 8200 Aarhus N, Denmark.
authors.forename: Jens Erik
authors.initials: JE
authors.lastname: Jensen
authors.affiliation: Plant and Environmental Sciences, University of Copenhagen, Hoejbakkegaard Alle 13, 2630 Taastrup, Denmark. Electronic address: jcs@plen.ku.dk.
authors.forename: Jens Carl
authors.initials: JC
authors.lastname: Streibig
mesh_terms: D001581:Benzothiadiazines / Q000032:analysis*; D004784:Environmental Monitoring; D005998:Glycine / Q000031:analogs & derivatives* / Q000032:analysis; D060587:Groundwater / Q000737:chemistry*; D057230:Limit of Detection; D010575:Pesticides / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D000097797:Glyphosate
chemical_list: D001581:Benzothiadiazines; D005998:Glycine; D010575:Pesticides; D014874:Water Pollutants, Chemical; D000097797:Glyphosate; C002003:bentazone
keywords: Contaminants; Drinking-water supply; Groundwater; Herbicides