Bioaccessible lead in soils, slag, and mine wastes from an abandoned mining district in Brazil

Abstract

We determined the amount of bioaccessible lead in samples of contaminated soils and in mining and refining wastes collected in the surroundings of a former smelter in a rural area in southeastern Brazil. Previous studies showed that some resident children and adults had blood Pb levels above recommended limits, but the contamination route was not established. The incidental ingestion of contaminated soils and dusts is considered to be a major route of lead uptake by humans. Bioavailability of heavy metals like Pb depends on solubility during digestion. We used in vitro tests that simulate human gastrointestinal (GI) media to measure the amount of soluble Pb under such conditions. Pb in soil and solid waste samples ranged from 0.03 to 4.1% and 1.2 to 15%, respectively. On average, 70% of the lead content was soluble in three different simulated gastric solutions (pH 1.5 and 1.7). For the same samples, lead solubility decreased to 2-22% when the pH was raised to pH 7 to approximate conditions found in the small intestine. These results indicate that if soils and dusts of the area are ingested, most of the lead will dissolve in the stomach, and part of it will remain soluble in the duodenum, i.e., would be potentially available for absorption. These findings may explain the high blood Pb levels previously reported.

Heavy Metals in Soil and Vegetables and Their Effect on Health

“…Dietary uptake pathway could be through crops irrigated with contaminated wastewater and have been reported to contain large amount of toxic heavy metals which may lead to health disorders in humans depending on the uptake of these metals into plant and consumed by animals or humans [6][7][8][9]. Consumption of metal contaminated vegetables may lead to a weakened immune system, intra-uterine growth retardation, impaired psycho-social behavior, high prevalence of upper gastrointestinal cancer and other disorders typically associated with malnutrition [10].…”

Total Excess Lifetime Cancer Risk Estimation from Enhanced Heavy Metals Concentrations Resulting from Tailings in Katsina Steel Rolling Mill, Nigeria

“…These heavy metals may get in to the human system through various exposure pathways such as direct ingestion of soils and dust inhalation. It is important to study the bioavailability of these heavy metals in order to understand the possible effect on biota and particularly on human health [7,8,[10][11][12][13][14][15]. Most metals are very toxic when they exist in excess and might be capable of causing major health effects such as developmental retardation, kidney damage, neurological and immunological effects as well as several types of cancer [16].…”

In Vitro Bioaccessibility of Lead in Artisanal Mining Contaminated Soils and Sediments from the Anka Area, NW Nigeria

“…However it is also influenced by the abundance of very labile residual lead oxide and lead carbonate minerals in the ores (Plumlee & Morman, 2011) and also confirmed by strong partitioning of lead into these phases seen during the SEPs experiments. Casteel et al (2006) Brazil and 75-80% for a certified reference soil, SRM 2710 by Bosso and Enzweiler (2008) using the PBET method. The mean lead bioaccessibility of 39.1% for urban soils in Guangzhou, China (Lu et al, 2011) is also within the range obtained here.…”

“…The pH range used in this work therefore falls within the fasted range and in general, a reduction in pH is expected to result in an increase in the dissolution of contaminant elements from an earth material. The effect of gastric pH is important when assessing the risk associated with ingestion of soil borne toxic elements, especially in economically deprived areas (Bosso & Enzweiler, 2008). In such areas, irregular feeding habits, often exemplified by the skipping of meals, means stomach pH remains low enough over long periods of time to ensure effective dissolution of contaminants incidentally ingested by children.…”