La prohibición de los perdigones de plomo es efectiva/The ban of lead-shot is effective

Radiografía de patos con perdigones en su molleja (ingeridos) y en el resto del cuerpo (disparo)/X-ray of ducks with lead shot in their gizzards (ingested) and in the rest of the body (fired) (IREC)

El perdigón de plomo fue prohibido en 2001 en los humedales españoles incluidos en la lista Ramsar, que enumera estas zonas de importancia internacional. Diez años más tarde, esta prohibición y la consecuente adopción del uso del perdigón de acero por parte de los cazadores ha empezado a dar sus frutos, según un estudio que publica la revista Environment International
“Lo más importante de nuestro trabajo es que se demuestra que el cambio de material –del perdigón de plomo al acero–, aun siendo una prohibición espacial parcial, ha reducido la intoxicación en las aves y la contaminación de la carne de caza”, declara Rafael Mateo Soria, del Instituto de Investigación en Recursos Cinegéticos (IREC), coautor del trabajo.
Los perdigones acumulados en los humedales, en muchas zonas con más de cien de estos proyectiles por metro cuadrado, permanecen en los sedimentos durante décadas. El principal daño que causan afecta a la propia salud de las aves. Al ingerir la munición, esta queda retenida en su molleja y se va deshaciendo de forma abrasiva en el estómago. El plomo liberado se absorbe y llega a los diferentes tejidos del animal.
En especies como el ánade azulón, en que un 30% de las aves cazadas a principios de los años 90 en el delta del Ebro habían ingerido perdigones de plomo, este porcentaje ha bajado hasta el 15%. La misma tendencia se observa en otras especies como el pato cuchara, la cerceta común o el porrón común.
Por el contrario, en el caso de los ánades rabudos cazados sigue siendo alarmante que más del 70% presenten perdigones en su molleja, un valor similar al observado hace tres décadas. El científico señala que para averiguar la razón del alto porcentaje de intoxicación en esta especie van comenzar el marcaje de aves con emisores. “Lo que sí sabemos es que por su tipo de dieta es una especie con alto riesgo de ingerir perdigones. No obstante, en otras que también tienen estos factores de riesgo, como el porrón europeo, su tasa sí ha disminuido al cambiarlos por los de acero”, añade.
Otro problema que origina el perdigón de plomo es la contaminación de la carne. Las trazas en los animales abatidos con este metal, incluso después de retirar los perdigones, superan los valores establecidos para la carne de consumo humano
Los investigadores quieren destacar que el cumplimiento de esta prohibición por parte de los cazadores ha sido muy alto y que han seguido cazando aves acuáticas en la misma cantidad después del cambio del plomo al acero. Sin embargo, la ley solo prohíbe el perdigón de plomo en humedales protegidos. Por este motivo, en los arrozales que los patos usan como zonas de alimentación sí están permitidos, lo que mantiene focos de contaminación para las aves y su carne.
Este estudio ha permitido valorar la efectividad de las medidas adoptadas por los países firmantes del Acuerdo para la Conservación de las Aves Acuáticas Migradoras de África-Eurasia (AEWA), un acuerdo para proteger las aves acuáticas en toda su ruta migratoria entre África y Eurasia y que han firmado una treintena de países europeos.

Ánade real o azulón/Mallard

Lead shot was forbidden in 2001 in Spanish wetlands on the Ramsar List of these areas of international importance. Ten years later, this prohibition -and the consequent use of steel shot by hunters- has started to bear fruit, according to a report in the journal ‘Environment International’.
“The most important part of our work is that it shows that, despite it’s still covering a partial area, the change of material from lead to steel shot has reduced waterfowl poisoning and the contamination of hunted meat,” says Rafael Mateo Soria of the Hunting Resources Research Institute (IREC) and co-author of the study.
Lead shot accumulating in wetlands, with over 100 per square metre in many areas, remains in the sediments for decades.Its main damage is to the health of waterfowl. When the shot is eaten it is retained in the gizzard and is worn down in the stomach, freeing lead that reaches the animal’s tissues.
In species such as the mallard, 30% caught at the start of the 1990s in the Ebro delta had ingested lead shot, a figure which has now dropped to 15%. The same trend has been seen in other species such as the northern shoveller, the Eurasian teal and the common pochard.
On the other hand, the case of the northern pintail caught continues to cause alarm since over 70% have shot in their gizzards, a rate similar to that seen three decades ago. The scientist notes that to discover the reason for the high percentage of poisoning in this species, they will start to fit birds with transmitters. "What we do know is that, because of its type of diet, this is a species with a high risk of ingesting shot. Nevertheless, in others that also have these risk factors, such as the common pochard, the rate has reduced after the change to steel shot," he added.
Another problem caused by lead shot is the contamination of meat. Even after lead shot was banned, the traces in animals caught with this metal exceed the limits set for meat for human consumption.
Researchers stress that the hunters’ compliance with this prohibition has been very high and that they have continued to hunt waterfowl in the same amount after the change from lead to steel. However, the law forbids lead shot in protected wetlands only. For this reason, lead shot is permitted in rice fields that ducks use as feeding areas, thus maintaining focuses of contamination for the birds and their meat.
This study has allowed the assessment of the effectiveness of the measures adopted by countries signing the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), an agreement to protect waterfowl along their entire migration route between Africa and Eurasia and signed by some 30 European countries.


Tomado de/Taken from Sinc Noticias (español/inglés)

Resumen de la publicación/Abstract of the paper
Reducing Pb poisoning in birds and Pb exposure in game meat consumers: The dual benefit of effective Pb shot regulation
Mateo, R., Vallverdú-Coll, N., López-Antia, A., Taggart, M.A., Martínez-Haro, M., Guitart, R., Ortiz-Santaliestra, M.E.
Environment International 63: 163–168, 2014.
Abstract
The use of lead (Pb) ammunition in the form of shot pellets has been identified as a Pb exposure risk in wildlife and their human consumers. We explore the hypothesis that Pb shot ban enforcement reduces the risk of avian Pb poisoning as well as Pb exposure in game meat consumers. We assessed compliance with a partial ban on Pb shot commencing in 2003 by examination of 937 waterbirds harvested by hunters between 2007 and 2012 in the Ebro delta (Spain). Prevalence of Pb shot ingestion was determined, as were Pb concentrations in liver and muscle tissue to evaluate the potential for Pb exposure in game meat consumers. Hunted birds with only embedded Pb shot (no steel) declined from 26.9% in 2007–08 to < 2% over the following three hunting seasons after ban reinforcement. Pb shot ingestion in mallards decreased from a pre-ban value of 30.2% to 15.5% in the post-ban period. Liver Pb levels were predominantly defined by the presence of ingested shot, whereas muscle levels were defined by the presence of both ingested and embedded shot. Only 2.5% of mallard muscle tissue had Pb levels above European Union regulations for meat (0.1 μg/g wet weight) in the 2008–09 season, when Pb shot ingestion prevalence was also at a minimum (5.1%). Effective restrictions in Pb ammunition use have a dual benefit since this reduces Pb exposure for game meat consumers due to embedded ammunition as well as reducing Pb poisoning in waterbirds.