Anthropogenic contamination is damaging the fragile Western Ghats making it necessary to understand the historical pollution. Radiocarbon dated sediment core covering the past 753 years is investigated to reconstruct the paleoclimate and paleotoxicity in Honnamanakere Lake, southern India. Increased sedimentation, weathering, organic carbon, and clay fraction during the medieval and modern warm periods indicate stronger southwest monsoon rainfall than during the little ice age. A decrease in silt content at the core location during warm periods suggests high lake levels. Cr, Cu, Zn, Pb, Hg except Ni content is increasing from bottom to top of the core. Multivariate statistics suggest natural sources for organic carbon and weathering products, agrochemical sources for Cr, Cu, Zn, atmospheric sources for Pb and Hg, and mixed sources for Ni. The enrichment factor and geoaccumulation index are increasing from the bottom to top of the core. Cr and Ni are significantly enriched and extremely contaminated and exhibit the most severe threat to the water body. The toxic risk index of Cu, Zn, Pb, and Hg suggests no toxic risk, Cr suggests low toxic risk and Ni suggests moderate toxic risk. The combined toxic risk of heavy metals suggests considerable to very high toxic risk. The mean probable-effects-levels quotient suggests heavy metals are posing a 49% toxic risk to the water body and its biota. In the sediment core, there is an increase in heavy metals enrichment, accumulation, and toxic risks during the past 300 years which is synchronous with the anthropogenic Industrial era.

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Understanding historical pollution is essential since anthropogenic contamination is destroying the Western Ghats' delicate ecosystem. The paleotoxicity in Honnamanakere Lake, southern India, is explored using a sediment core that has been radiocarbon dated and spans the last 753 years. With the exception of Ni, the core's Cr, Cu, Zn, Pb, and Hg contents rise from bottom to top. According to multivariate statistics, the sources of Cr, Cu, and Zn are agrochemical; the sources of Pb and Hg are atmospheric emissions; and the sources of Ni are mixed. From the bottom to the top of the core, the geoaccumulation index and enrichment factor both rise. The most serious threat to the water body comes from Cr and Ni, which are greatly enriched and highly contaminated. The toxic risk indices for Cu, Zn, Pb, and Hg indicate negligible toxic risk, low toxic risk for Cr, and moderate toxic risk for Ni. The water body and its biota are at a 49% hazardous risk from heavy metals, according to the mean probable-effects-levels quotient. Heavy metal enrichment, accumulation, and toxic risks have increased in the sediment core during the past 300 years, coinciding with the anthropogenic Industrial age.