Influence of particle size and total organic carbon on the distribution of polybrominated diphenyl ethers in landfill soils: assessment of exposure implications

Background

The selection of soil fraction is an important influencing factor to accurately determine human exposure risk to toxic chemicals in the environment. The present study evaluated the concentrations of prevalent polybrominated diphenyl ethers (PBDEs) in different size fractions of soil from a landfill site and the factors that influence their distribution in the soils.

Method

Samples were fractionated into size fractions; between 150–250 and 45–150 μm (after initial sieving through a 250 μm sieve) and, thereafter, PBDEs were extracted using a mixture of toluene-dichloromethane and subsequently cleaned with a multilayer silica gel/Pesticarb/sodium sulphate column and analysed using GC-MS.

Results

The sum of seven PBDE congeners (BDE-28, -47, -100, -99, -154, -153 and -183) ranged from 7.08 to 10.8 ng g⁻¹ with a total median of 7.32 ng g⁻¹, and from 7.00 to 8.77 ng g⁻¹ with a total median of 7.21 ng g⁻¹, corresponding to size fractions 150–250 μm and 45–150 μm, respectively. BDE-183 was predominant in both soil fractions. A significant correlation was observed between ∑₇PBDEs concentrations and total organic carbon (TOC), particularly for particle size 150–250 μm (r² = 0.829, p < 0.05).

Conclusion

The study revealed that PBDE concentrations did not automatically increase with decreasing particle size, and as such, PBDE-treated consumer goods and consequent abrasions of flame retardant-containing materials could be likely sources. The study also clarified that selecting soil fractions arbitrarily for exposure risk assessment may lead to inconclusive results. The study results, therefore, have important inferences for estimating flame retardant chemical exposure.