More flame retardants found in urban peregrine falcons than their country cousins.

Park, J-S, A Holden, V Chu, M Kim, A Rhee, P Patel, Y Shi, J Linthicum, BJ Walton, K Mckeown, NP Jewell and K Hooper. 2009. Time-trends and congener profiles of PBDEs and PCBs in California Peregrine falcons (Falco peregrinus). Environmental Science and Technology doi: 10.1021/es901600h.

Falcons that make their home in some of California's largest cities carry more flame retardant pollutants in them as compared to those that preside in rural areas, finds a study that measured the chemicals in the birds' eggs.

The eggs from peregrine falcons living in the state's biggest urban areas have five times more flame retardants than eggs collected from nests in the countryside or near the Californian coast. The findings suggest that the health of urban raptors is at greater risk from exposure to flame retardants than those that live in less populated environments.

Polybrominated diphenyl ethers (PBDEs) have been used in numerous products since the 1970s because they make rugs, furniture and drapery less flammable. Like PCBs, their heavy use, uncontrolled disposal and persistence have caused widespread environmental contamination and concerns over potential health effects in wildlife and humans.

The PBDE chemicals are lipid-loving, and will concentrate through food chains to high levels in top predators. Levels of PBDEs have been increasing in humans and wildlife but decreased production and bans of some types in recent years in North America may reverse this trend in the future.

Peregrine falcons (Falco peregrinus) feed on other birds like ducks, pigeons and starlings, and are susceptible to accumulation of persistent pollutants because of their position at the top of the food chain. Indeed peregrine falcon populations declined in the 1950s and 1960s because high DDT levels thinned their egg shells, preventing the chicks from hatching.

Though this species is no longer listed as endangered in the US, there may be ongoing threats to their health from exposure to flame retardants. These chemicals are known to affect reproduction and the immune system in other bird species.

In this study, 90 peregrine falcon eggs and 7 chicks were collected during 22 years (between 1986 and 2007) from California cities – including San Diego, San Francisco and Los Angeles (from nests on top of office buildings) – and from the coast and countryside, areas well away from any large urban centers. These samples were analyzed for PBDEs and PCBs.

Concentrations of the PBDEs were five times higher (10.1 parts per million) in eggs from nests in cities than either the coast or countryside (2.38 and 1.61 parts per million, respectively). This is likely because of the higher use and disposal of these chemicals in urban areas. Levels of these flame retardants in the eggs also tripled over the two decades of the study. In contrast, PCB levels in the eggs did not change in any of the regions over the same time period.

Levels in the peregrine falcon eggs were similar to what is known to cause effects on growth and development in other falcon species. The results of this study show that peregrine falcon living in urban areas are at greater risk from exposure to flame retardants than ones living far away from populated areas.