A couple of years after the Chernobyl incident of April 26 1986 there was an increase in thyroid cancer in children exposed
to the radioactive fallout. As the exposed children age, the number of thyroid cancer cases continues to increase. These cancers are likely caused by exposure to the major fallout product 131I and to a lesser extent other short-lived iodine isotopes. Follow-up of individuals exposed to
radiation during the atomic bomb drops on Japan suggests that the
consequences of the Chernobyl incident may not be fully appreciated for decades to come. This review covers the health outcomes and international response to the Chernobyl incident.The most common disease caused by the Chernobyl incident to date is thyroid cancer among exposed children. The incidence may actually increase in the future since the tumor grows slowly. The number of deaths due to thyroid cancer is low since the disease is curable. Thyroid cancer reports among exposed adults is increasing as well but most of the scientific attention is focused on exposed children.To date, approximately one-third of the liquidators and plant workers have died from radiation-related sickness. These individuals received acute, high, whole body radiation exposure.Stresses such as fear and mistrust of authority are common among survivors of the incident. These stresses have led to an increase in substance abuse and cigarette smoking. The health consequences of these behaviours, disease and death, are indirect measures of the health outcomes of the Chernobyl accident. These outcomes are often ignored but are likely significant.Several children of fathers exposed to fallout have increased DNA mini-satellites but the health consequences of this aberration are not known. This uncertainty is one example of our evolving understanding of radiation poisoning. Current theory does not account for genomic instability or the bystander effect. Moreover, the dose-response relationship for radiation exposure is being re-evaluated and data suggests that at low concentrations the response is supralinear. Even if such a relationship was known the health consequences to Chernobyl survivors would be unclear since whole-body and tissue-specific radiation doses is not known or imprecise. Other disorders such as birth defects and leukemias have not been conclusively linked to the incident. The fallout may increase the incidence of breast cancer since breast epithelia concentrates iodine. Indeed, the long-term consequences cannot be estimated because of the uncertainties surrounding our current understanding of radiation poisoning.Several years after the incident the USSR sought help from the World Health Organization (WHO) and the International Atomic Energy Agency (IAEA). These organizations were asked to assess environmental and health outcomes. The IAEA summarized their findings in a 1991 report. At the time of the report it was not generally accepted that 131I was carcinogenic and the IAEA has yet to recognized the increase in thyroid cancer. The WHO began investigating health outcomes in 1991 and initiated humanitarian and fund-raising efforts. Their efforts were re-inforced by many nations and non-governmental agencies.The efforts to aid Chernobyl investigations were complicated by the breakup of the Soviet Union and disorganization among the agencies involved. Humanitarian and research efforts by the WHO were hindered by the different leaderships of the newly formed countries (Belarus, Ukraine, the Soviet Republic). The WHO had internal disagreements and Misappropriation of funds while some branches suffered from a lack of funding. This disorganization discouraged other agencies from cooperating.Early research focused on the rare childhood thyroid cancer incidence, potential mechanisms of carcinogenesis and biomarkers to help in compensation cases. The carcinogenicity of 131I isnow accepted, but a biomarker for the cancer has not been identified. The most common Chernobyl-related cancer has been papillary but its incidence is increasing and other causes cannot be excluded.The United Nations Educational Scientific and Cultural Organization initiated a psychosocial support effort in 1991. This program effectively offered support to children and adults in effected areas through the establishment of rehabilitation centres. The United Nations Development Program began a needs assessment program in 2001. This program identified and relocated individuals who continued to suffer disproportionately. The IAEA began a Chernobyl Forum to investigate the environmental and health consequences and a summary of their findings was published in 2005. The report is designed to downplay the negative effects of the incident such as the number of deaths. The number of future deaths attributable to the incident cannot be known since an accident of this magnitude is unprecedented. The public may perceive that the WHO and IAEC downplayed the health and environmental consequences and this may be the most negative outcome of the Chernobyl follow-up. Long-term studies over the lifetime of survivors must be initiated and fully-funded to ascertain the scope of health consequences.