Health Risk Assessment of Lead Ingestion Exposure by Particle Sizes in Crumb Rubber on Artificial Turf Considering Bioavailability
Sunduk Kim ; Ji-Yeon Yang ; Young-Wook Lim ; Dong-Chun Shin ; In-Young Yeo ; Ho-Hyun Kim
환경독성보건학회지, Vol.27 : e20120005, 2012
The purpose of this study was to assess the risk of ingestion exposure of lead by particle sizes of crumb rubber in artificial turf filling material with consideration of bioavailability.
This study estimated the ingestion exposure by particle sizes (more than 250 um or less than 250 um) focusing on recyclable ethylene propylene diene monomer crumb rubber being used as artificial turf filling. Analysis on crumb rubber was conducted using body ingestion exposure estimate method in which total content test method, acid extraction method and digestion extraction method are reflected. Bioavailability which is a calibrating factor was reflected in ingestion exposure estimate method and applied in exposure assessment and risk assessment. Two methods using acid extraction and digestion extraction concentration were compared and evaluated.
As a result of the ingestion exposure of crumb rubber material, the average lead exposure amount to the digestion extraction result among crumb rubber was calculated to be 1.56×10-4 mg/kg-day for low grade elementary school students and 4.87×10-5 mg/kg-day for middle and high school students in 250 um or less particle size, and that to the acid extraction result was higher than the digestion extraction result. Results of digestion extraction and acid extraction showed that the hazard quotient was estimated by about over 2 times more in particle size of lower than 250 um than in higher than 250 um. There was a case of an elementary school student in which the hazard quotient exceeded 0.1.
Results of this study confirm that the exposure of lead ingestion and risk level increases as the particle size of crumb rubber gets smaller.
Keywords: Artificial turf, Bioavailability, Crumb rubber, Exposure assessment, Lead.
Go to:AbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONFiguresTablesNotesACKNOWLEDGEMENTSReferencesINTRODUCTION
Toxic substances contained inside of artificial turf, who's utility has recently been increasing, and its negative effect on children's health are on the rise as a social issue. In particular, for heavy metals, polycyclic aromatic hydrocarbon and, volatile organic compounds contained inside of artificial turf filling, there is a fear that ingestion exposure could happen through direct absorption of rubber powder or indirect flow into the human body when rubber-stained hands are moved to the mouth. The hazard to humans and to the environment, when rubber powder is used as artificial turf filling, is still uncertain, but doubts and interest in its potential dangers have been growing in various countries in and out of Korea. In the case of the U.S.A., the research presented by the Office of Environmental Health Hazard Assessment claimed, after toxicity assessment results related to ingestion of rubber ingestion based on research into children's gastrointestinal tract digestion, in the case of rubber powder being ingested for a short period of time, it was possible to confirm the danger level of some heavy metal materials . National Broadcasting Company of U.S.A. reported absorption of lead according to the simulation .
It is known that lead has a strong toxicity even when just a small amount of lead enters inside the human body. In the case that the human body is exposed to lead, the smaller the particle size and the younger the age of the exposure group, the higher the absorption rate inside the body, and it is known that only a portion of lead that is not absorbed is discharged from the human body. In addition, lead that enters the body is absorbed instead of calcium. Thus, children who need a lot of calcium, even when exposed to the same amount of lead as adults, an even larger amount of lead that exceeds the level of adults is absorbed inside by the children's body. Also, compared to the adults, children have a more active metabolism, which leads to 3-7 times quicker absorption of lead than in adults. Since the absorption rate or the latency period of lead is big among children, children have a bigger body load than adults. In the case of children, they are more sensitive to the toxicity of lead, and because lead induces damages to the kidney, liver, nerves and immune system, management of lead is very important.
Bioavailability is a value which shows how much pollutant can negatively affect humans and living organisms, and it is used to show how much is absorbed after the chemical substance enters the human body, is absorbed and is circulated. Most of the time, experiments about bioavailability are used to assess the heavy metals inside the soil, and Netherlands Rijksinstitut voor Volksgezondheid en Milieu (RIVM) is suggesting various methods of experiment. Following this, based on artificial digestion simulation research, research that applies the potential bioavailability of the ingestion exposure inside rubber powder is in progress [3-5].
Until now, examples of exposure and risk assessment examples related to rubber powder used for artificial turf are mostly inhalation exposure, skin exposure, and ingestion exposure. Among these exposure examples, research about ingestion exposure is a supposition about direct ingestion, and there is research in progress that estimates the exposure claim that states that rubber powder may be swallowed from artificial turf during exercise . However, this estimate only supposes the worst condition. It is necessary to consider the possibility that small-sized particles, that exist in the powder state due to deterioration of rubber powder, can be unconsciously inhaled in the case that a person is exposed to hazardous substances while doing activities on the artificial turf. In the case of hazardous substances being exposed to the human body, the absorption rate inside the body can show differences in absorption rate according to the particle size. Researche done to compare the difference between the particle sizes due to ingestion exposure in soil or in food, and according to the in vitro digestive fluid extract experiment related to the particle size of the soil, the smaller the particle size, the higher the concentration [7,8]. Compared to the particles that are big, particles that have a small grain diameter, by increasing the unit surface area per mass, obtain characteristics that are more usable, biologically [9,10].
According to the content method and elution test method of artificial turf filling per each particle size, various age groups who used playgrounds with artificial turf were investigated, and the purpose of this study was to estimate the human risk level through lead ingestion exposure assessment.