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Kids are at higher risk from toxic metals in dirt than previously thought

Harold Mandel's picture
Kid playing in dirt

Kids are vulnerable to exposure to toxic agents all around them. Due to the sensitive nature of their developing bodies and minds many toxic agents pose a potentially very serious threat to the well being of kids. Soil is one place the risk to kids from toxic metals is often underestimated.

Japanese researchers have investigated the risk assessment of direct soil ingestion and metals adhered to children's hands at playgrounds reported the journal Risk Analysis. They noted that the quantity of heavy metals in soil is generally measured after 2-mm sieving in Japan to determine risk assessment of direct soil ingestion.

The researchers studied the relationship between the size of soil particles and:

1: The quantity of heavy metals in soil

2: The particle-size distribution of soil adhered to children's hands

3: The risks of direct intake of soil considering the particle sizes ingested

There has been an underestimation of the risk of direct soil intake

It was observed that smaller particles had a tendency to contain more heavy metals than larger ones. Furthermore, the particle size of about 90 percent of the soil particles from playgrounds adhered to children's hands was less than 100 µm. They concluded the 2-mm sieving in preparation for measuring heavy metal content caused an underestimation of the actual risk of direct soil intake.

The researchers investigated the amount of heavy metals on children's hands after they played outside. It was observed that various metals and soil were adhered to the hands of the kids.It was determined that the amount of soil which adhered could be estimated from the concentration of metals. The researchers said in order to develop accurate risk assessment, the particle-size distribution of soil which is ingested and more detailed scenarios of soil intake are clearly necessary.

Japanese researchers developed a new approach to assess kid's soil related risks

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The bottom line is according to Japanese researchers at Kyoto University’s Research Reactor Institute and colleagues approaches which are currently used may be underestimating the risk which is posed to kids by toxic metals which they are exposed to while they are playing outdoors reports the Society for Risk Analysis.

The Japanese researchers instituted a new more careful approach in order to study how much dirt and associated metals adheres to kid’s hands. They discovered that many heavy metals including zinc, chromium and lead among others adhere more to smaller soil particles than to the larger particles which are generally employed in soil exposure studies. This new more careful approach seems better for a more accurate assessment of children’s soil related risks.

Soil ingestion is a significant pathway of toxic substance exposure in kids

The U.S.Environmental Protection Agency and its counterparts in other countries have shared concerns about children’s ingestion of contaminants through soil. This study offers new insights into better potential protections for kids and the risks which are posed by soil related exposures. This is significant because soil ingestion is one of the most significant pathways through which kids are exposed to toxic substances. There is a higher rate of exposure from soil in kids than adults because of their hand to mouth behavior.

More careful methods for assessing soil ingestion by kids are necessary

According to the researchers in order to make an accurate evaluation of the risk it is important to understand the size of the soil particles children directly ingest. These researchers found that about 90 percent of soil particles remaining on the hands of kids were less than 100 µm. This supports their position that laboratories and researchers should transition to the more careful method used by the researchers in order to prevent underestimating children’s risks. This is necessary in order to protect children who ingest soil with metals while playing in various high exposure areas such as:

1: Dirt playgrounds

2: Near hazardous waste sites

3: In areas with heavy vehicle traffic

The researchers also highlighted that it is important to be very careful about kids who have pica wherein they display an unusual habit of intentionally ingesting large amounts of soil and the associated contaminants.

This study highlights the often overlooked high risk of exposure to highly toxic metals in kids playing in dirt. In view of the realization that standard methods of analysis appear to have been underestimating the risk of this exposure our kids have been more vulnerable to this exposure than they should be. A better understanding of this exposure along with refined testing methods for heavy metal exposure should lead to more aggressive efforts to protect kids from this exposure.