The rollout of electric vehicles and photovoltaic panels is essential to mitigate climate change. However, they depend on technology-critical elements (TCEs), which can be harmful to human health and whose use is rapidly expanding, while recycling is lacking. While mining has received substantial attention, in-use dissipation in urban areas has so far not been assessed, for example, corrosion and abrasion of vehicle components and weather-related effects affecting thin-film photovoltaic panels. Therefore, the question arises to which extent TCEs dissipate during use and which potential non-occupational human health impacts could occur. We assessed the available information on urban in-use dissipation and human health concerns and conducted exploratory modeling of in-use technology stocks, in- and outflows, and in-use dissipation of neodymium, dysprosium, lanthanum, praseodymium, cerium, gallium, germanium, and tellurium contained in 21 vehicle and renewable energy technologies, for Vienna, Austria. In prospective scenarios, TCE dynamics in a trend-continuation vis à vis official city policy plans and a more ambitious transition scenario were then assessed. We find that electrifying the vehicle fleet without demand-reduction is the main driver of TCE consumption, effectively doubling cumulative end-of-life outflows to 3,073 [2,452–3,966] t and cumulative in-use dissipation to 9.3 [5.2–15.7] t by the year 2060. Sufficiency-based measures could reduce demand and in-use dissipation well below levels with continued trends, thus highlighting the need to combine decarbonization with demand-reducing measures. These results help assess potential future in-use dissipation dynamics and inform discussions about potential public health hazards associated with exposure to TCEs accumulating in the urban environment.