Assessment of Heavy Metal Pollution, Radionuclides, and their Health Implications: A Case Study for Murree, Pakistan

Abstract

Soil pollution is directly related to the urbanization of an area. Murree is a renowned tourist attraction in Pakistan. In recent years, Murree has been developing rapidly, raising pollution levels. In this study, elemental analysis of soil from urban areas of Murree was performed using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and an elemental analyzer, while the activities of naturally occurring radionuclides (NORMs) were also measured using Gamma Spectrometry. It was found that the average metal concentrations decreased in the following order: Ca > Al > Fe > Mg > Ti > Mn > Ba > Zn > Zr > V > Cr > Pb > Ni > Cu > Co > As > Sn. Various parameters, such as enrichment factor, geo-accumulation index, pollution and integrated pollution index, and ecological risk factor were calculated to assess the soil pollution levels. These parameters revealed low to moderate contamination at most of the sites and high pollution levels at one site. Principal Component Analysis (PCA) and correlation matrix revealed various sources for these metals namely burning of coal and wood, petrol and diesel vehicles, urban waste and geogenic. Carbon and nitrogen concentrations showed that the soil in the region is of poor quality and is unsuitable for optimal crop and plant growth. Non-carcinogenic and carcinogenic health hazards related to Cu, Pb, As, Ni, Cr, Mn, Ba, Zn and Co, exposure via three pathways (inhalation, dermal contact, and ingestion) were calculated for both adults and children; namely Average Daily Dose (ADD), Hazard Quotient (HQ), Hazard Index (HI) and Cancer Risk for Lifetime Exposure (CRLE). The highest HI value observed in adults was 0.023 for Ni and in children 0.207 for Co. In both adults and children, the HI values for each metal were less than 1, indicating no appreciable health risk. However, children have HI values for each metal that were 8–10 times higher, respectively, than adults. Only Cr in children posed a carcinogenic risk with the total cancer risk for lifetime exposure value CRLETotal = 3\(\times\)10-4. Specific activities and health hazards associated with gamma exposure from natural radionuclides were also quantified. The average specific activities of Ra-226, Th-232, K-40 and Cs-137 in Bq/kg were 26.8 ± 14.4, 17.4 ± 4.9, 495.9 ± 82, 8 ± 3.2 respectively. The mean values for Radium Equivalent (Raeq), Outdoor External Dose (Dout) Indoor External Dose (Din) Annual Outdoor Effective Dose (Eout) Annual Indoor Effective Dose (Ein) and Total Lifetime Cancer Risk (LCRtotal) are 38.2 Bq/kg, 43.5 nGy/h, 83 nGy/h, 0.05 mSv/y, 0.4 mSv/y, and 1.53\(\times\)10-3 respectively. The spatial distribution of heavy metals and natural radionuclides was studied using interpolation to quantify their distribution geographically in Murree. This study demonstrates that some urban areas of Muree, near the city center are highly polluted.