Contaminants, global change and cold regions

Abstract

Perhaps the first example of climate change and contaminants interacting with fatal consequences occurred during the Franklin expedition of 1845-1848. Franklin's group, which entered the Canadian Archipelago hoping to discover a Northwest Passage during a cool period of climate (the end of the so-called 'little ice age' (Bradley and Jones 1993)), was doomed to failure simply by poor ice conditions. They brought with them food that was contaminated by lead from soldering in early experiments with canning (Keenleyside, et al. 1997). The harsh environmental conditions, which stalled progress and prevented retreat, also made game hard to find leading to a strong reliance on the food they brought. Although there remains controversy over what role lead poisoning might have played in Franklin's demise, this example well illustrates how the environment and contaminants can operate together; toxicity is often a consequence of two or more factors, any one of which might not cause irreparable harm by itself, and sometimes there is a shortcut pathway, or vector, that provides a surprise. How global change might impact semi-volatile organic contaminants was considered almost a decade ago (Harner 1997), but the focus was mainly on the effect of temperature rise. Intuitively, warmer temperatures enhance volatility, force chemicals back out of water, and perhaps increase degradation rates. This sounds like good news and McKone et al. (1996) concluded from model results that exposure of aquatic foodwebs to HCB (hexachlorobenzene) would be reduced should warming occur. However, in Alpine and Arctic regions, the important change is not likely to be temperature rise per se, but rather phase change (ice-water, snow-rain) and change in systems (foodwebs, organic carbon cycle, hydrological cycle, ocean/ice interaction). These system changes alter transfers between me dia and contaminant magnifying processes within the environment. Recent detailed reviews of change in the Arctic and inferences of what these changes might mean for contaminants reveal a surprising number of ways that climate variation and climate change can affect pathways, and how these pathway changes then alter risks to ecosystems (Macdonald, et al. 2003; 2005). Here, it is not my intention to repeat these lengthy reviews but rather to provide a synopsis of how global change may alter the risks to humans and ecosystems from semi-volatile contaminants in cold regions.