The most effective way to evaluate the extent and effect of mercury pollution is through a comprehensive monitoring program. Monitoring programs are also the only way to assess the environmental response to mercury emissions reductions. With that in mind, a team of scientists has developed a vision for mercury monitoring in North America. Published in the journal Environmental Science & Technology, this program calls for a net work of 200 new long-term monitoring sites across different ecosystems, as well as 10 sites for intensive investigation.

Long-term network sites

The long-term net work sites would measure six indicators:
1. Atmospheric wet deposition (weekly);
2. Surface soil sampling for elemental mercury and methylmercury (twice per year);
3. Surface water measurements of elemental and methylmercury (twice per year);
4. Yearling fish mercur y concentrations (twice per year);
5. Piscivorous/commercial fish mercury levels (annually); and
6. Wildlife mercury levels (annually).

Intensive study sites

Monitoring at the intensive study sites would involve additional detailed atmospheric, watershed, aquatic and biota sampling including:
1. Atmospheric mercur y by species (continuously);
2. Mercury evasion (monthly);
3. Watershed yield from surface and groundwater (monthly);
4. Long-term sediment depth mercury profiles (every 3-5 years);
5. Mercury and methylmercur y profiles throughout the water column (twice per year);
6. Phytoplankton and algae mercury levels (monthly); and
7. Zooplankton and bent hic invertebrate sampling (monthly).

Although significant efforts have been made over the past decade to understand the many connections bet ween emissions that occur across continents and the human
and ecological effects, many questions remain. The first step in answering these questions is the development, funding and implementation of a national (and international) mercury monitoring program. Since change is already occurring and it is critical to assess how changing emissions affects the environment and human health, this program should be initiated as soon as possible.