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Urinary Naphthol as a Biomarker of Exposure: Results from an Oral Exposure to Carbaryl and Workers Occupationally Exposed to Naphthalene

Health and Safety Executive, Harpur Hill, Buxton SK17 9JN, UK
Academic Editor: David Bellinger
Received: 27 October 2016 / Revised: 28 December 2016 / Accepted: 30 December 2016 / Published: 6 January 2017
(This article belongs to the Collection Risk Assessment of Pesticide Exposure)
PDF [725 KB, uploaded 6 January 2017]


Urinary naphthol is an established human biomarker used for assessing both occupational and environmental exposure. However, 1-naphthol is a metabolite of the insecticide carbaryl while both the 1- and 2-isomers are metabolites of naphthalene. Thus, urinary 1-naphthol levels will reflect combined exposure to both substances, particularly at environmental levels. The interpretation of biomarkers is aided by knowledge of levels following well-characterised exposure scenarios. This study reports urinary 1-naphthol levels in five volunteers administered an oral dose of carbaryl at the acceptable daily intake (ADI, 0.008 mg/kg). The elimination half-life was 3.6 h and the mean 1-naphthol level in 24 h total urine collections, normalised for a 70 kg individual, was 37.4 µmol/mol creatinine (range 21.3–84.3). Peak levels in spot-urine samples were around 200 µmol/mol creatinine. For comparison, 327 post-shift urine samples obtained from 90 individual workers exposed occupationally to naphthalene had 1-naphthol levels from below the limit of detection (<LoD) to 1027 µmol/mol creatinine (median = 4.2, mean = 27.2). The 2-naphthol levels ranged from <LoD to 153 µmol/mol creatinine (median = 4.0, mean = 8.1). Background ranges have been reported for urine naphthols in several populations, with upper limits between 10 and 20 µmol/mol creatinine. The data reported here suggest that environmental exposure to carbaryl and naphthalene in these populations is well controlled. View Full-Text
Keywords: carbaryl; exposure assessment; human biomonitoring; naphthalene; naphthol carbaryl; exposure assessment; human biomonitoring; naphthalene; naphthol

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Sams, C. Urinary Naphthol as a Biomarker of Exposure: Results from an Oral Exposure to Carbaryl and Workers Occupationally Exposed to Naphthalene. Toxics 2017, 5, 3.

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