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This study reports a spatiotemporal characterization of formaldehyde and acetaldehyde in the summer and winter of 2017 in the urban area of Shiraz, Iran. Sampling was fulfilled according to EPA Method TO-11 A. The inverse distance weighting (IDW) procedure was used for spatial mapping. Monte Carlo simulations were conducted to evaluate carcinogenic and non-cancer risk owing to formaldehyde and acetaldehyde exposure in 11 age groups. The average concentrations of formal-dehyde/acetaldehyde in the summer and winter were 15.07/8.40 μg m−3 and 8.57/3.52 μg m−3, respectively. The formaldehyde to acetaldehyde ratios in the summer and winter were 1.80 and 2.43, respectively. The main sources of formaldehyde and acetaldehyde were photochemical generation, vehicular traffic, and biogenic emissions (e.g., coniferous and deciduous trees). The mean inhalation lifetime cancer risk (LTCR) values according to the Integrated Risk Information System (IRIS) for formaldehyde and acetaldehyde in summer and winter ranged between 7.55 × 10−6 and 9.25 × 10−5, which exceed the recommended value by US EPA. The average LTCR according to the Office of Environmental Health Hazard Assessment (OEHHA) for formaldehyde and acetaldehyde in summer and winter were between 4.82 × 10−6 and 2.58 × 10−4, which exceeds recommended values for five different age groups (Birth to <1, 1 to <2, 2 to < 3, 3 to <6, and 6 to <11 years). Hazard quotients (HQs) of formaldehyde ranged between 0.04 and 4.18 for both seasons, while the HQs for acetaldehyde were limited between 0.42 and 0.97.

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High nitrate concentration in drinking water has the potential to cause a series of harmful effects on human health. This study aims to evaluate the health risk of nitrate in groundwater resources of Hormozgan province in four age groups, including infants, children, teenagers, and adults, based on the US EPA methodology and Monte Carlo technique to assess uncertainty and sensitivity analysis. A Geographic Information System (GIS) was used to investigate the spatial distribution of nitrate levels in the study area. The nitrate concentration ranged from 0.3 to 30 mg/L, with an average of 7.37 ± 5.61 mg/L. There was no significant difference between the average concentration of nitrate in all study areas (p > 0.05). The hazard quotient (HQ) was less than 1 for all age groups and counties, indicating a low-risk level. The HQ95 for infants and children in the Monte Carlo simulation was 1.34 and 1.22, respectively. The sensitivity analysis findings showed that the parameter with the most significant influence on the risk of toxicity in all age groups was the nitrate content. Therefore, implementing a water resources management program in the study area can reduce nitrate concentration and enhance water quality.

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