Health risk posed by enriched heavy metals (As, Cd, and Cr) in airborne particles from Witwatersrand gold tailings

Abstract

Severe episodes of windblown dust from mine tailings storage facilities (TSFs) are a common phenomenon on the Witwatersrand, especially during the spring windy season. For communities around TSFs, such events pose health and environmental challenges. This paper reports on health risk assessment using US Environmental Protection Agency (US EPA) risk assessment methods for heavy metal elements in windblown dust from TSFs on the central and east Witwatersrand. Samples of surface material from these TSFs were analysed for heavy metal content using inductively coupled plasma-mass spectrometry (ICP-MS). From a range of 30 heavy metals analysed, only As, Cd, Cr, Pb, and U were enriched by a factor of two or more above the average crustal composition and at concentrations that could be of possible health concern-elements present in the range of a few parts per billion (ppb) or lower were ignored. As, Cd, Cr, Pb and U were selected for a comprehensive risk assessment from exposure through airborne routes, mainly considering inhalation and ingestion. Ambient exposures were based on a worst-case measured episode of 540 μg m -3 (24-hour average), which was projected over each day of an annual exposure for the hours for which the wind speed was above the threshold for dust generation. US EPA risk assessment methods were used to determine the inhalation and ingestion hazard quotients and hazard indices for adults and children. The sum of the hazard indices was assessed to be below the non-cancer benchmark (hazard indices 1.0) considered to be acceptable for a lifetime exposure. The total risk for both exposures (inhalation and the ingestion) was within the range of 1 per 1 000 000 to 100 per 1 000 000-taken as 'acceptable risk' by the US EPA for adults and children. These results represent the first quantitative health risk assessment of the hazard posed by heavy metals in windblown mine tailings dust on the Witwatersrand goldfield. mine tailings, dust, airborne particles, health risk, inhalation, ingestion heavy metals, arsenic, cadmium, chromium.

Dust Deposition Impacts at a Liquidated Gold Mine Village: Gauteng Province in South Africa

“…It is expected to observe this trend as it was found by Maseki et al [ 8 ] that As, Pb, U and Au are highly enriched in the West Witwatersrand Basin. This is owing to the increased uranium and gold content of the Dominion Reef mined in the Basin.…”

“…Other scholars calculated a wind speed of 9 m/s as the speed required to initiate erosion from tailings storage facilities in New Brunswick and Ontario, Canada. Table 1 summarises all the data inputs for the ADDAS model [ 8 ].…”

“…A number of TSFs are unlined and unrehabilitated, posing an environmental challenge, including water contamination by acid mine drainage (AMD), air pollution by windblown dust as well as particulate emissions [ 8 ]. In 2013, the West Rand District Environmental Management Framework estimated approximately 21.21 t/day particulate emissions from TSFs in the Merafong Municipality, the largest emitter in the West Witwatersrand Basin [ 9 ].…”

A Review: Assessment of Trace Metals in Municipal Sewage and Sludge: A Case Study of Limpopo Province, South Africa

“…Here, the trace metals may originate from metal fabrication industry [1], road runoff stormwater drains that are connected to municipal sewage plants [2][3][4], tannery industry [5], and from domestic households where zinc/copper scrubbers are used [6]. Trace metals have been known to originate from active and abandoned mine tailings, and these trace metals enter the aquatic environment during rainy events [7][8][9] or windy events [10]. Some of the non-point pollutions are as follows: trace metals also leaching from sewage sludge spread on farmland [11] and discharge of bath water to the terrestrial environment where there is leaching to the aquatic environment.…”

Heavy Metals Pollution Characteristics and Health Risk Assessment of Farmland Soils and Agricultural Products in a Mining Area of Henan Province, China

“…If the tailings are discharged at random, heavy metals will be released into surrounding soils, streams, and groundwater mediated by erosion, weathering, and leaching over a long duration, which may pose serious environmental threats to the surrounding area [10][11][12][13]. As a kind of persistent potentially toxic pollutant, heavy metals can easily accumulate in excessive amounts in soils and sediments [14][15][16][17]. As excess amounts of metals enter the pedosphere, many nearby farmland mining areas can be contaminated by heavy metals, which threaten the safety of agricultural products and lead to human exposure [18][19][20][21].…”