Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

Primary Producers
Commonly reported effects of Pb on vascular plants include the inhibition of
photosynthesis, respiration, and/or cell elongation, all of which reduce plant growth. However, it
was noted that studies of other effects on plant processes such as maintenance, flowering, and
hormone development had not been conducted; therefore, no conclusion could be reached
concerning effects of Pb on these processes.
The EPA (U.S. Environmental Protection Agency, 1986a) concluded that most plants
experience reduced growth when Pb concentrations in soil moisture (the film of moisture
surrounding soil particles in the root zone of soil) exceed 2 to 10 mg/kg. It also was concluded
that most plants would experience reduced growth (inhibition of photosynthesis, respiration, or
cell elongation) in soils of ∃10,000 mg/kg when soil composition and pH are such that
bioavailability of Pb in the soil is low (see Section AX7.1.3 for details on factors affecting
bioavailability of Pb in soil). Acid soils or soils with low organic matter tend to increase Pb
bioavailability and would inhibit plants at much lower Pb concentrations (e.g., as low as