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Ambient Air Quality and Human Health Risk Assessment of Heavy Metals in a Potentially Toxic Silver-Polluted Environment

Unyeawaji Brownson Ntesat, David Ojadi, Chinwendu Emeka, Reuben Nwomandah Okparanma

Research Journal of Ecology and Environmental Sciences 5(1); 10.31586/rjees.2025.1058 - January 01, 2025

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Abstract

Silver nanoparticles (Ag+NPs) contamination in the environment is a serious concern. This study investigated selected heavy metal (Ag+, Cd2+, Cr2+ and Pb2+) concentrations at different sampling points to assess the risk to human health (infants, children, and adults). To do this, an enclosed area (laboratory) of 12.6 m X 8.5 m (107.1 m2) was clearly marked at different coded distances of S1, S2, S3, and S4 representing 2, 4, 6, and 8 m, while unpolluted atmosphere at 50 m away without Ag+NPs served as the control (S5). The silver fireworks were allowed to burn for an approximate 00h03m30s at each sampling points using a high-volume air sampler mounted at the Environmental Engineering Departmental Laboratory, Rivers State University, with windows and doors closed to simulate indoor conditions. Samples were digested using a mixture of analytical-grade nitric acid, analytical-grade hydrochloric acid and analyzed to evaluate the levels of heavy metals by atomic absorption spectrophotometry. The Ag+ result at S1 shows 30,000 µg/cm3, S2 was 29,000 µg/cm3, while S3 was 28000 µg/cm3 and then S4 was 13,000 µg/cm3. These results exceeded the permissible values of the United States National Ambient Air Concentration for rural, urban and industrial areas (0.0005, 0.004 and 0.6 µg/cm3, respectively). The result for the control (S5) (0.037 µg/cm3) was within the maximum allowable value. Results from other heavy metals such as Cd were 1000, 743, 401, 153, 0.001 µg/cm3, Cr was 5000, 4000, 3729, 2960, 0.002 µg/cm3, Pb was 0.048, 0.041, 0.035, 0.034 and 0.01, µg/cm3, respectively. However, higher values of Ag+, Cd, and Cr indicated a higher propensity for the metals to be toxic (bioavailable). In addition, the assessment of the potential health risk posed by these metals proved contaminated and harmful. Visitors recorded high values in exposure concentration (EC) and low values in average daily dose (ADD).

Figure 1. Indoor Geo-Mapping of the Study Area, Rivers State, Nigeria

Figure 2. (a) Unused Silver fireworks, (b) burning fireworks, (c) used silver fireworks and (d) High volume air sampler

Figure 3. Average Daily Dose of Heavy Metals Concentrations at Various Stages of Human life over Distance in Toxic Ag+ Nanoparticle Polluted Environment for Residents [S1 = 2 Meters, S2 = 4Meters, S3 = 6 Meters, S4 = 8Meters, and S5 = Unpolluted Environment (Control); Error bars on the chart represents percentages].

Figure 4. Exposure of Heavy Metals Concentration at Various Stages of Human life over Distance in Toxic Ag+ Nanoparticle Polluted Environment for Residents. [S1 = 2 m, S2 = 4 m, S3 = 6 m, S4 = 8 m, and S5 = Unpolluted Environment (Control); Error bars on the chart represents percentages].

Figure 5. Average Daily Dose of Heavy Metals Concentration at Various Stages of Human life over Distance in Toxic Ag+ Nanoparticle Polluted Environment for Visitors. [S1 = 2 m, S2 = 4 m, S3 = 6 m, S4 = 8 m, and S5 = Unpolluted Environment (Control); Error bars on the chart represents percentages].

Figure 6. Exposure of Heavy Metals Concentration at Various Stages of Human life over Distance in Toxic Ag+ Nanoparticle Polluted Environment for Visitors. [S1 = 2 m, S2 = 4 m, S3 = 6 m, S4 = 8 m, and S5 = Unpolluted Environment (Control); Error bars on the chart represents percentages].

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