**1. Introduction**

Pollution by heavy metals has gradually worsened in Asian, African, and South American countries, partly due to the excessive use of pesticides for growing crops which may in turn lead to the pollution of groundwater and well water. An investigation by the Food and Agriculture Organization (FAO)/United Nations Environment Programme (UNEP)/World Health Organization (WHO) suggests that the number of patients with pesticide poisoning is approximately 1–5 million annually, and several thousand cases are fatal. In some Asian countries, wells reserved for drinking water were dug below the acceptable levels to avoid pesticide pollution, and consequently, many inhabitants developed arsenic poisoning [1, 2]. Rivers and soils are also polluted by industrial wastes in those countries. In particular, wastes from metallurgy and mining industries contain various heavy metal ions, and wastes from leather industries contain cadmium and chromium. These wastes are typically exhausted and discarded in nearby rivers and in the air due to the lack of posttreatment equipment or strictly controlled landfill sites, resulting in detrimental groundwater and soil pollution.

Additionally, environmental pollution by heavy metals has resulted in serious disease. In Japan, four historic cases of metal pollution occurring predominately in the 1950s have been reported, which include "ouch-ouch" disease and Minamata disease. In 1910, a mining company eliminated cadmium waste into a nearby river. The inhabitants who drank directly from the river or ingested food grown along the riverbanks developed cadmium poisoning and exhibited symptoms such as spine and leg pain and fragile bones. In another case of heavy metal poisoning, the improper elimination of methylmercury waste into a nearby river resulted in neuroparalysis (Minamata disease) among the locals. Recent problems due to heavy metal pollution in some countries may be more serious than the previous incidences in Japan. Therefore, it is critical to remediate polluted areas as quickly as possible in order to decrease the risk of disease.

Lead is an important heavy metal because it is widely used to produce electronics, crystal glasses, and batteries. The annual consumption of lead has been increasing at a high rate in China due to the increased demand for cars and power-assisted bicycles according to the rapid economic growth. Recently, a relationship between high blood lead levels and lead pollution in lead mining areas has been proclaimed as a serious problem [3]. Some reports have suggested that many children living in the areas near mining industries developed symptoms of lead poisoning [4]. Therefore, the control of lead emissions and remediation of soil polluted from lead are crucial.

The purpose of this chapter is to assess both the causes of lead pollution and the efficiency of bioremediation by plants and microorganisms. First, the author investigated the causes of lead contamination, and the results suggest that soil pollution from lead occurred particularly in the areas where metallurgy and mining industries were present. Then, the author determined whether phytoextraction is a practical method for lead remediation in these areas. Finally, the author proposed a novel lead remediation process which employs microorganisms. The proposed process, the LIM method, combines immobilization with landfarming. As the treatment period in the LIM method is much shorter and lead can be readily collected from the soil, the process may be a viable alternative to phytoextraction.
