The Gulf of Mexico was irreparably assaulted in spring 2010 when the Deepwater Horizon, an offshore drilling rig, exploded, killing 11 workers. The vessel sank on April 22, leaving the oil well gushing at the seabed, creating the most massive oil spill in U.S. history. The industry was unprepared to deal with such a disaster, and it took nearly two months before the oil could be stopped. More than 750-million litres poured into the Gulf of Mexico, and this was followed by seven-million litres of chemical dispersants intended to break it up.
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The Gulf has long been home to many of the most productive fisheries in the U.S., primary catches being crustaceans (shrimp) and molluscs (oysters, clams and other shellfish). Most of the fisheries re-opened in fall 2010, and the U.S. Food and Drug Administration introduced risk criteria and established thresholds for allowable levels of toxins.
Yes. You are reading that correctly. It's not about whether the seafood caught from the Gulf of Mexico has toxins in it. There is no question that it does. It's about determining an appropriate level of toxin ingestion for the average human diet.
The main contaminants from an oil spill are polycyclic aromatic hydrocarbons (PAHs). PAHs are carcinogens. They are known to accumulate in seafood because many marine organisms are unable to process them. Internal levels of PAHs increase as one moves up the food chain from filter-feeding animals to predators, and the toxins remain active for extremely long periods. Based on data from the Exxon Valdez oil spill, researchers have shown that PAHs are detectable in shellfish for up to 13 years after contamination1. These compounds are associated with stunted growth, anemia and kidney disease in humans2. Napthalene is one of the most frequently detected PAHs in seafood, and this compound is strongly associated with cancer risk. Studies have shown dose-related nasal and respiratory cancers in rats, as well as associations with laryngeal and colorectal cancer in humans3.
A recent report examining the "acceptable" levels of toxins in the diet set forth by the U.S. FDA details many aspects of how these values are unacceptably high2. The allowable quantities do not take into account the more vulnerable members of the population such as pregnant women and young children. Since they are lipid soluble, PAHs have no trouble crossing the placenta and reaching a developing fetus. Exposure to PAHs during pregnancy has been shown to cause significant increases in DNA aberrations, low birth weight and intrauterine growth restriction.4,5,6
Will I be eating any seafood from the Gulf of Mexico? Likely not, for a few reasons: I do not live close to the area, and I won't actively seek out products that come from there. Folks who live near the Gulf of Mexico do not have the luxury of that choice. As I said above, it's not about whether or not they will consume contaminated seafood; it's about guessing a "safe" amount to consume. I'm lucky to live here in British Columbia where the waters are free from oil rigs and pipelines. Oh wait...
1Thomas RE, Lindeberg M, Harris PM, Rice SD. 2007. Induction of DNA strand breaks in the mussel (Mytilus trossulus) and clam (Protothaca staminea) following chronic field exposure to polycyclic aromatic hydrocarbons from the Exxon Valdez spill. Mar Pollut Bull 54(6):726-732.
2Rotkin-Ellman M, Wong KK, Solomon GM. 2012. Seafood contamination after the BP Gulf oil spill and risks to vulnerable populations: a critique of the FDA risk assessment. Environ Health Perspect 120:157-161.
3NTP (National Toxicology Program). 2011. 12th Report on Carcinogens. Research Triangle Park, NC:National Toxicology Program. Available: http://ntp.niehs.nih.gov/ntp/roc/twelfth/roc12.pdf [accessed 15 December 2011].
4Choi H, Jedrychowski W, Spengler J, Camann DE, Whyatt RM, Rauh V, et al. 2006. International studies of prenatal exposure to polycyclic aromatic hydrocarbons and fetal growth. Environ Health Perspect 114:1744-1750.
5Dejmek J, Solanský I, Beneš I, Lenícek J, Šrám RJ. 2000. The impact of polycyclic aromatic hydrocarbons and fine par¬ticles on pregnancy outcome. Environ Health Perspect 108:1159-1164.
6Orjuela MA, Liu X, Warburton D, Siebert AL, Cujar C, Tang D, et al. 2010. Prenatal PAH exposure is associated with chromosome-specific aberrations in cord blood. Mutat Res 703(2):108-114.