Halogenated pollutants in terrestrial and aquatic bird eggs: converging patterns of pollutant profiles, and impacts and risks from high levels20 May 2015
We investigated the presence, levels, relationships, and risks of HCHs, DDTs, chlordanes, mirex, PCBs, and brominated flame retardants (BFRs) in terrestrial and aquatic bird eggs from an area in South Africa where DDT is used for malaria control. We found one of the highest ΣDDT levels reported this century; 13 000 ng/g wm (wet mass) in Grey Heron eggs which exceeds critical levels for reproductive success (3000 ng/g wm) calculated for Brown Pelicans, with a no-effect level estimated at 500 ng/g wm. Even higher ΣDDT levels at 16 000 ng/g wm were found in House Sparrow eggs (possibly the highest ever recorded for sparrows), with a maximum of 24 400 ng/g wm. Significant eggshell thinning in Cattle Egrets (33% between thickest and thinnest) was associated with increased levels of p,p′-DDT and p,p′-DDE. There were indications of unknown use of DDT and lindane. Relative to DDT, PCBs and BFRs levels were quite low. Ordinated data showed that different terrestrial pollutant profiles converged to a homogenised aquatic profile. Converging profiles, high levels of DDT in heron and sparrow eggs, and thinning eggs shells, indicate risk and impacts at release, in the aquatic environment, and in between. If characteristic life-strategies of birds in warm areas (e.g. longer-lived and fewer eggs per clutch) increases the risk compared with similar birds living in colder regions when both experience the same environmental pollutant levels, then malaria control using DDT probably has more significant impacts on biota than previously realised. Therefore, risk assessment and modelling without hard data may miss crucial impacts and risks, as the chemical use patterns and ecologies in Africa and elsewhere may differ from the conditions and assumptions of existing risk assessment and modelling parameters. Consideration of other findings associated with DDT from the same area (intersex in fish and urogental birth defects in baby boys), together with the findings of this study (high levels of DDT in bird eggs, eggshell thinning in the Cattle Egrets, and the apparent absence of breeding piscivore birds in the sprayed area) are strongly suggestive of negative impacts from DDT spraying for Malaria control. Our data presents strong arguments for an expedited process of replacing DDT with sustainable methods.