January 21, 2020

expert reaction to study of plant uptake of lead from solar panels

Research, published in Nature Communications, reports that lead from some solar cells is more likely to be absorbed by plants than other lead contaminants are. 

Prof Christopher Collins, Professor of Environmental Chemistry at the University of Reading, said:

“The researchers have used a very conservative scenario. They assume all the lead from the solar panel leaches into the soil and remains there.  The reality is that the lead would leach very slowly from the solar panel and maybe moved down the soil profile across time.

“The workers state that plants are the main link that transfers heavy metals from ground to food and thus the human body. Using the exposure model developed by the UK Environment Agency, the predominant pathway for lead ingestion is actually from soil in hand to mouth activities when harvesting the vegetables – and such an activity would not be undertaken by all people ingesting the contaminated food.

“Overall, I am not convinced this would be a problem in the real world. There is a sensible message to adopt safer metals when producing solar panels and also ensuring the risk assessment is done using the appropriate compound configuration.”

Prof Christos Markides, Head of the Clean Energy Processes (CEP) Laboratory in the Department of Chemical Engineering at Imperial College London, said:

“This is an interesting study concerning the environmental impact of lead in perovskite solar cells, a photovoltaic technology that has attracted significant attention recently owing to its excellent performance and promise of lower cost compared to conventional and other alternatives. It is of note because it explores the impact on plants of the use of lead in such solar cells and provides evidence that this is something that should be considered with great care.

“Concerns relating to the widespread deployment of lead-based perovskite solar cells have been raised for some time, given that these toxic materials are soluble in water, so contamination can lead to environmental but also health issues once they enter the food chain.

“I would consider it a bold assumption that the entire lead content of a solar panel is being dispersed to the ground below, however the study demonstrates that we may need to conduct further testing to fully understand the impact of these materials on our environment, especially over large areas and long periods of deployment. In parallel to this, research into (lead-free) tin-based perovskite solar cells has been on-going to provide alternatives, but these have not yet shown the level of performance achieved with lead. In either case, non-trivial stability issues remain that act to limit the lifetime of such panels. With the growing need and continuing trend to secure our energy from renewable sources, and especially given the important role of solar energy, it is vital that further research is done on these and other technologies to overcome challenges and to ensure that these are affordable, safe and sustainable.”

Prof Andrew Meharg, Professor of Biological Sciences at Queen’s University Belfast, said:

“This study has a number of important limitations. I can’t see many circumstances where lead from solar panels would get into soil at concentrations to cause concern, especially in a crop context. Lead contamination of soils is multiple and extensive, and in cases extreme, globally, from a wide range of industrial and domestic activities, yet lead in crops is not really a concern due to lead’s poor mobility in soils, its limited uptake by and  restricted translocation within plants. The lead from the peroskovite lead is only 0.1% of panels, and only doubles in the edible parts (leaves) of one plant (mint), tested on one soil. The break-up and leaching scenarios to soils of solar panels needs investigated, this was not conducted here, To state that all lead in solar panels should be replaced, with another toxic and problematic element tin, from such limited findings is not warranted without further extensive testing in a range of actual soils that have been contaminated in situ by disused solar panels.

‘We should be worried about lead in halide perovskites’ by Junming Li et al. was published in Nature Communications at 4pm UK TIME on Tuesday 21 January 2020. 

DOI: 10.1038/s41467-019-13910-y

Declared interests

Prof Meharg: I have no conflicts of interest.

Prof Markides: Nothing to declare.

Prof Collins: I have no conflicting interests