Transport and release of chemicals from plastics to the environment and to wildlife

Abstract

Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2'-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g(-1) to microg g(-1). Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub microg l(-1) to mg l(-1) and were correlated with the level of economic development.

Figure 1.

Schematic appearance and concentration of a hydrophilic (left), moderate hydrophobic (middle) and hydrophobic (right) phthalic acid diester (solid lines) and respective monoester (dashed lines) in landfill leachate (modified from Jonsson 2003). The appearance of the diester is correlated to its depletion in the phthalate-containing product.

Figure 2.

Degradation of a phthalic acid diester (solid line) to its corresponding monoester (dashed line) and phthalic acid (dotted line) in a landfill developing from acidogenic to stable methanogenic phase. Also, the methane production is included (reproduced with permission from Jonsson 2003).

Figure 3.

Concentrations of endocrine-disrupting chemicals (EDCs) in leachates from waste disposal sites in Asia.

Figure 4.

Relationship between BPA concentrations in leachates from waste disposal sites and per capita GDP of Asian countries (r² = 0.66, n = 26). Leachates from municipal waste disposal sites in capital and other major cities are plotted. See figure 3 for the symbols of the countries. Data are for countries except Japan.

Figure 5.

Comparison of o-xylene desorption data and one-compartment diffusion model fits as well as predictions of o-xylene desorption rates from PVC and HDPE spheres of different diameters. Desorption data were measured after six months of equilibration in ultrapure water.

Figure 6.

Effect of polymer type on sorbed toluene mass remaining and released per gram of sorbent. Lines represent model fits for sorption equilibrium liquid-phase concentration (C_e) of 100 µg l^–1, K_p = 70.7 (µg kg^–1)(l µg^–1) for HDPE and K_f = 1663 (µg kg^–1)(l µg^–1), and n = 0.864 for PVC (Wu et al. 2001). The particle diameters of HDPE and PVC were 0.5 and 0.14 mm, respectively.

Figure 7.

Concentrations of PCBs (ng g⁻¹ pellet) in beached plastic pellets. Polychlorinated biphenyl concentration = sum of concentrations of CB nos 66, 101, 110, 149, 118, 105, 153, 138, 128, 187, 180, 170, 206.

Figure 8.

Concentrations of organic contaminants in marine plastic debris (fragments). Solid diamond: The North Pacific Central Gyre; open circle: Japanese coast of the Pacific Ocean. Polychlorinated biphenyls: sum of concentrations of CB nos 66, 101, 110, 149, 118, 105, 153, 138, 128, 187, 180, 170, 206; DDE: concentration of p, p′-dichlorodiphenyl dichloroethene; PAHs: sum of concentrations of phenanthrene, anthracene, methylphenanthrenes (substitution position: 3, 2, 9, 1), fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene and coronene; PBDEs: concentration of BDE nos 3, 7, 15, 17, 28, 71, 49, 47, 66, 77, 100, 119, 99, 85, 126, 154, 153, 138, 183; NP: concentration of nonylphenols; OP: concentration of octylphenol; BPA: concentration of bisphenol A.

Figure 9.

Schematic illustrating the additional effects of plastics in the transport of phenanthrene: (a) sorption of phenanthrene to clean plastic in sediment resulting in (b) subsequent accumulation of phenanthrene in the sediment, compared with (c) sorption of phenanthrene to plastic in the SML and subsequent sinking resulting in (d) accumulation of phenanthrene in the sediment. Note that (c)→(d) results in higher sediment phenanthrene concentrations than (a)→(b). Although not shown in the schematic, sorption to the sediment also occurs (reproduced with permission from Teuten et al. 2007). Copyright 2007 (American Chemical Society).

Figure 10.

(a) Distribution coefficients (K_d) for sorption of phenanthrene to UV-treated plastics from seawater. (b) Amount of phenanthrene-sorbed plastic required in sediment (0.2% organic carbon) to increase lugworm tissue concentration by 80%, compared with plastic-free sediment, predicted using equilibrium partitioning as described previously (Teuten et al. 2007). Plastics were exposed to a UV lamp for 9 and 16 days, equivalent to 208 and 460 days in natural sunlight. Note that plastic concentrations in sediment are well below the maximum reported amount of 81 ppm (Reddy et al. 2006).

Figure 11.

Loads of total PCBs in chicks. Closed circles: cumulative load from fish (Japanese sand lance: Ammodytes personatus); dotted line: load from plastic resin pellets.

Figure 12.

Time-course of PCBs in preen gland oil of the chicks during the feeding experiment: (a) total PCBs* and (b) lower chlorinated congeners**. *Total PCBs: sum of CB nos 8, 5, 28, 52, 44, 90, 101, 110, 77, 118, 132, 153, 138, 160, 187, 128, 180, 170, 190, and 206; **lower chlorinated congeners: sum of CB nos 8, 5, 18, 28, 52, 44, 66, 95. Polychlorinated biphenyl concentrations are normalized to those on day 0 on each series. Closed symbols and solid lines: plastic-feeding setting; open symbols and dotted lines: control setting. Replicate chicks no. 1 (closed square), 5 (cross), 8 (closed diamond), 10 (closed circle), 14 (closed triangle), 4 (open circle), 9 (open triangle), 18 (open diamond) were analysed. For chicks 1, 5, 8, 4, 18, samples were analysed on day 0 and day 7 only.