Abstract <p>The correlation between the natural radioactivity, pH, and microbial load in rock samples collected in Perumbakkam, a suburb of Chennai, Tamil Nadu, India, was studied. Gamma spectrometry was employed to quantify the concentrations of radionuclides (²³⁸U, ²³²Th, and ⁴⁰K), and associated radiological risk was appraised through indices such as Ra_eq, AEDE, and hazard indices. The concentration of microbes was evaluated by means of the pour plate technique, and pH of an aqueous suspension was determined. Pearson correlation coefficients and Thompson-style plots were then used to explain the relationships between the radiological, chemical, and biological parameters. The results show a strong association of the radiological variables and distributed, locally specific impact with the pH and microbial activity. Site W3 had highly increased radiology levels, showing possible environmental and farming issues. The paper highlights the need for an evaluative combination of sustainable land use and radiology safety.</p>