Organic-inorganic Pb halide perovskite (HaP)-based solar cells have shown great promise as a sustainable and economic way of electricity generation as its power conversion efficiencies skyrocketed to over 25% [1] within a decade of its introduction. To date, all the best-performing HaPs contain Pb and are fairly soluble in water.  Pb is considered a hazardous heavy metal with major health concerns affirmed by various international organizations with recommended restricted levels of Pb in potable water (10-15 µg/L) [2]. One of the challenges of this technology is its potential environmental hazard of accidental Pb leached from broken cells/modules due to failure of encapsulation/packaging, vandalism, hail, storm, and subsequent rain. Quantifying the environmental hazard of accidental Pb²⁺ leaching, i.e., the reactivity and mobility of Pb²⁺ leached from HaP-based solar cells into the soil and from there to groundwater, was the goal of this research. Pb²⁺ originated from inorganic salts was previously found to remain in the upper soil layers due to adsorption. However, Pb-HaPs contain additional organic and inorganic cations, and competitive cation adsorption may affect Pb²⁺ retention in soils. We measured, analyzed and simulated the penetration depth profile of Pb²⁺ from HaPs and non-HaP sources into 3 types of agricultural soil under typical rain conditions, and its adsorption mechanism to the soil was described [2]. Most of the leached Pb²⁺ was found to be retained already in the first cm of the soil columns, and subsequent rain events do not induce Pb²⁺ penetration below the first few cm of soil surface irrespective of its sources and types of soil [3]. At conditions relevant to outdoor damage to HaP-based solar cells, it was found that the Pb²⁺ content retained by the topsoil is at least 100 times smaller than that of their maximum adsorption capacity. Surprisingly, organic co-cations from the dissolved HaP are found to enhance the Pb²⁺ adsorption capacity, compared to non-HaP-based Pb²⁺ sources. Our findings suggest that Pb²⁺ from damaged HaP-based solar cells is unlikely to contaminate groundwater, hence mass-scale utilization does not imply an environmental hazard. Panel installation over soil types with improved Pb²⁺ adsorption, regular inspection and removal of only the contaminated topsoil, are sufficient means to make the technology innocuous.