Transactions - FBI - Vysoká škola báňská - Technická univerzita ...

Transactions of the VŠB - Technical university of OstravaSafety Engineering SeriesVol. VI, No. 2, 2011p. 32 - 38Materials and methodsEvaluation of the health risks from As exposurein kindergarten playground soil included thefollowing steps: sampling and chemically analyzingthe soil samples, selecting the exposure model, andcalculating the exposure and characterizing thehealth risk.Sampling and Chemical analysisDuring the 2002 - 2007 period soil sampling wascarried out at the playgrounds of 413 kindergartensin 38 towns in the Czech Republic. Surface soilsamples were collected and processed accordingto Standard Operating Procedures that had beendeveloped within the framework of the study. Thesoil samples were collected down to a depth of10 cm from five sampling sites at each outdoorplayground. The sampling sites were selectedtaking into account the most frequent locations ofthe children’s stay on the playground. After removalof extraneous material (e.g. stones, glass fragments,roots, etc.), all five samples were homogenized ina plastic container of adequate size. Contents of thecontainer were emptied onto a PE sheet and thena circle (pie) was created with a thickness of 1 - 2 cm,which was subsequently divided into four quadrants.Two opposite quadrants were amalgamated (theother two were removed) in a clean PE containerand re-homogenized. By additional quartering thesample mass was reduced to 1 kg. The resultingsample was taken to an accredited laboratory foranalysis. Determination of As in the soil samplewas performed by a hybrid technique using X-rayspectrometry with secondary emission and an energydispersive semiconductor detector.Exposure modelTo assess the health risks in children exposed toAs in playground soil, a residential exposure scenariofor ingestion of soil and soil dust, and for the dermalcontact with the soil were selected in accordancewith previously established methodologies (EPA,1997; EPA, 1999; EPA, 2001; EPA, 2004; EPA,2005). Deterministic and probabilistic methodswere used for the health risk assessment. Due toa relatively regular distribution of the kindergartensacross the areas of the monitored towns, it wasassumed that the level of contamination of surfacesoils in the urban agglomerates was homogeneousand corresponded to a set of identified values. Inassessing the risk of cancer, it was also assumed thatthe concentration of As in the soil for the duration ofexposure was constant.Parameter values and calculation of theexposureOral exposure - the average daily non-carcinogenicoral dose of As (CDI n) for ingestion of soil and soil dustwas calculated according to as follows: CDI n[mg.kg -1 .day -1 ] = (CS x CF x EF x B x IR x ED)/(BW x AT)The average daily carcinogenic oral dose of As (CDI n)for ingestion of soil and soil dust was calculated asfollows: CDI c[mg.kg -1 .day -1 ] = (CS x EF)/AT x [(ED cx IR c)/BW c) + (ED ax IR a)/BW a)]. The values ofthe parameters used for the calculation of the dailyoral non-carcinogenic and carcinogenic doses of Asfrom the contaminated soil were determined froma literary background (Ministry of the Environment,2005; EPA, 1991; EPA, 1997; EPA, 2004).Dermal exposure - the average daily dermalnon-carcinogenic doses of As and the daily dermalcarcinogenic doses of As for the dermal contactwith the soil were determined as follows: CDI d[mg.kg -1 .day -1 ] = (CS x FI x AF. ABS x SA x ED xEF)/(BW x AT). The values of the parameters usedfor the calculation of the dermal non-carcinogenicand carcinogenic doses of As from the contaminatedsoil were determined from a literary background(EPA, 2004).Characterization of the risk - the deterministicmethod of evaluation of the health riskThe level of non-carcinogenic risk is expressedas a coefficient of hazard (hazard index - HI). Itis calculated as: HI = CDI n/RfD where RfD is thereference dose measured in mg.kg -1 .day -1 . Thethreshold value equals 1. To calculate the oralexposure to As, an RfD of 0.0003 mg.kg -1 .day -1 wasused and for the dermal exposure, an RfD value of0.000123 mg.kg -1 .day -1 was used. An overall riskof toxicity was expressed by the sum of the valuesof the risk of oral and dermal exposures (EPA,2005). The rate of individual lifelong cancer riskis expressed by: ILCR = CDI c·CSF, where ILCR isan individual lifetime cancer risk. CDI c, measuredin mg.kg -1 .day -1 , is the average daily carcinogenicdose and CSF, measured in mg.kg -1 .day -1 , is a risk ofcancer indication (cancer slope factor). The value ofCSF for oral exposure to As is 1.5 mg.kg -1 .day -1 andfor the dermal exposure to As is 3.66 mg.kg -1 .day -1 .An overall risk of cancer from exposure to As fromsoil is determined by the sum of the values of risksarising from oral and dermal exposures (EPA, 2005).The threshold value of ILCR ranged from 1x10 -4 to1x10 -6 depending on the size of the study subjects.33