Chromium: another threat to whale health?
Wise Sr., JP, R Payne, SS Wise, C LaCerte, J Wise, C Gianios Jr., WD Thompson, C Perkins, T Zheng, C Zhu, L Benedict and I Kerr. 2009. A global assessment of chromium pollution using sperm whales (Physeter macrocephalus) as an indicator species. Chemosphere doi:10.1016/j.chemosphere.2009.02.044.
Researchers sampling skin from sperm whales around the world found the animals have the highest levels of the metal chromium in their bodies of any marine mammal tested to date. The levels in the skin of the whales are similar to those found in lung tissues of humans with chromium-induced lung cancer and may be an additional health threat to the already endangered species.
Little is known about chromium in the world's ocean despite its link to human cancers. The metal can also affect the reproductive system and behavior of other mammals, according to animal studies.
The metal has been rarely measured in marine mammals and never before at a global scale as was done in this study. Concentrations in these endangered whales were higher than those found in a study on beached sperm whales from the North Sea and between 10 to 40 times higher than levels found in the skin of minke whales and bottlenose dolphins.
This once abundant species is now endangered because of historical overharvesting by whalers. As one of the ocean’s top predators, sperm whales are very polluted, and this, too, may inhibit their recovery. They accumulate high levels of many persistent contaminants, such as chlorinated pesticides and industrial chemicals, in their tissues.
But less is known about the metals they carry and the risks posed by them to sperm whales' health. The findings from this study show the whales contain high levels of chromium and suggest there may be cause for concern.
In fact, the authors strongly state that chromium "pollution in the marine environment is significant and that further study is urgently needed."
Oceans are contaminated with chromium from both natural and human sources. Dusts carried in air currents move chromium from the land to the ocean. Much of the metal in our environment comes from human activities, such as the burning of fossil fuels and from industries that smelt metals, tan leather and manufacture textiles.
Between 2000 and 2005, researchers collected non-lethal skin samples (biopsies) from 361 sperm whales (217 females and 114 males) from 16 different sites in the Pacific, Indian and Atlantic oceans and the Mediterranean Sea. Chromium was detected in all but two of the whales. The average concentration for all samples was 8.8 ppm (range of 0.9 to 122 ppm).
Chromium levels were highest in sperm whales from the Kiribati and Sechelles Islands in the Pacific and Indian Oceans, respectively. The levels were lowest in animals near the Canary Islands in the Atlantic Ocean and near Sri Lanka in the Indian Ocean. Females and juvenile males had higher levels than the adult males sampled.
