CONTAMINATED SOIL, DUST NEW PATHWAYS to lead poisoning in children; Risk increases in summer months
Exide has been poisoning Frisco’s air with tons of toxic lead emissions for more than four decades, and it is known to have some of the highest lead emissions in the United States. But it’s not just the air that Exide has made toxic and dangerous, it is the land and soil surrounding the smelter. Research now shows that soil, and the dust from such lead-contaminated soil – which can be found on all surfaces that can be touched, including playground equipment, etc., – is a proven pathway for lead poisoning in children. And it is now well-known fact that is there is no safe level of lead exposure.
Gabriel M. Filippelli and Mark A. S. LaidlawDepartment of Earth Sciences, Indiana University–Purdue University Indianapolis (IUPUI), Indianapolis, IN – Winter 2010
delves into the role contaminated soil and dust play lead poisoning of children, and it also points out that such risk increases during summer months. Below are key highlights from the report:
“Recent research into the causes of seasonal variations in blood-lead levels among children has confirmed the importance of soil in lead exposure.
The primary cause of chronic lead loading in urban youth is their continued contact with dust derived from lead-enriched inner-city soils. This new paradigm of the exposure pathway of children to lead, which has been verified by recent research into the causes of seasonal swings in children’s blood lead levels, points to a relatively simple and cost-effective way toward reducing the lead load for urban youth.
In particular, the continued poisoning of urban youth from the very dirt and soil upon which they live is the key to a new emerging paradigm—namely, that the continuing source of lead exposure to children is lead-enriched soils, and particularly dust resuspended from these soils,
Based on this multiple regression model and recently published results from several other American cities (Laidlaw and Filippelli 2008), it appears that the seasonality in children’s blood-lead levels is controlled by exposure to lead dust originating from contaminated soils and suspended in the air when several weather-related environmental conditions are present: temperature is high, soil moisture is low, and atmospheric PM10 is elevated (Figure 2). When temperature is high and evapotranspiration maximized, soil moisture becomes low, lead-enriched PM10 dust disperses in the urban environment and is manifest by elevated lead-dust loading. In this case, exposure is via increased dust loads in homes and on contact surfaces, with ingestion being the uptake mechanism and toddlers at greatest risk due to their behavior (crawling, tactile exploration, hand-to-mouth behavior).
Because resuspension of lead from contaminated soil appears to be driving seasonal child blood-lead fluctuations, lead contaminated soil in and of itself may be the primary driving mechanism of child blood-lead poisoning in the urban environment.
However, the seasonal deposition of lead-enriched dust and its ingestion by children may not be the only factor driving the observed seasonal patterns in blood-lead levels. Recent work indicates a potential role for increased sunlight-induced vitamin D synthesis in the summer, which increases gastrointestinal lead absorption and skeletal lead mobilization at least in children from 4–8 years of age (Kemp et al. 2007). In fact, multiple interacting causes may be at play, with factors including lead-enriched soil deposition, as well as age, race, sunlight exposure, and diet.
In summary, a newer paradigm of urban lead loading has emerged, one that helps to explain continued chronic lead poisoning and seasonal patterns in blood-lead levels of children. Unlike discrete point sources like lead paint and industrial contact, which are still responsible for most cases of acute lead poisoning, diffuse soil lead is the main avenue for urban lead loading of children. The diffuse soil lead comes from several sources, including leaded gasoline and degraded lead-based [End Page 43] paints, but in a sense the source no longer matters: because of the ability of surface soils to retain lead, these soils themselves have become the new risk factor for children’s health in lead-loaded cities.”