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Modeling of methyl isothiocyanate air concentrations associated with community illnesses following a metam‐sodium sprinkler application
Author(s) -
O'Malley Michael,
Barry Terrell,
VerderCarlos Marylou,
Rubin Andrew
Publication year - 2004
Publication title -
american journal of industrial medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.7
H-Index - 104
eISSN - 1097-0274
pISSN - 0271-3586
DOI - 10.1002/ajim.20037
Subject(s) - medicine , eye irritation , irritation , toxicology , zoology , immunology , biology
Background A series of illnesses occurred in Earlimart, CA on November 13, 1999 following a metam‐sodium sprinkler application to a potato field on the southern edge of the town. Methods Case information was obtained from direct interviews, from illness complaints filed with state or county agencies, or from illness reports filed by community physicians for 173 subjects. Air concentrations of the by‐product methyl isothiocyanate (MITC) during the episode were estimated based upon the Industrial Source Complex Short‐Term (ISC3) air dispersion model, estimates from prior metam‐sodium monitoring studies, and data from weather stations in two adjoining communities. Results Weather station data indicated that the November 13th incident corresponded with a temperature inversion at approximately 5:00 p.m. and a shift in the direction of prevailing wind from northwest to southeast. On the edge of Earlimart, 1‐hr time weighted average (TWA) MITC concentration estimates ranged from 0.5 to 1 ppm. Of the 173 subjects, 170 had MITC‐compatible symptoms, including eye or upper respiratory irritation (77.6%), non‐specific systemic symptoms (64.7%), and lower respiratory symptoms (20.0%). 78.2% were exposed within 0.5 miles of the northern edge of the treated field where average 1 hr MITC concentrations exceeded the 800 ppb ocular irritation threshold. Conclusions ISC3 modeling is a useful means of evaluating MITC concentrations for illness episodes when industrial hygiene assessment is not possible. Am. J. Ind. Med. 46:1–15, 2004. © 2004 Wiley‐Liss, Inc.