Academic journal article Environmental Health Perspectives

Occurrence of [.Sup.210]po and Biological Effects of Low-Level Exposure: The Need for Research

Academic journal article Environmental Health Perspectives

Occurrence of [.Sup.210]po and Biological Effects of Low-Level Exposure: The Need for Research

Article excerpt

BACKGROUND: Polonium-210 ([.sup.210]Po) concentrations that exceed 1 Bq/L in drinking-water supplies have been reported from four widely separated U.S. states where exposure to it went unnoticed for decades. The radionuclide grandparents of [.sup.210]Po are common in sediments, and segments of the public may be chronically exposed to low levels of [.sup.210]Po in drinking water or in food products from animals raised in contaminated areas.

OBJECTIVES: We summarized information on the environmental behavior, biokinetics, and toxicology of [.sup.210]Po and identified the need for future research.

METHODS: Potential linkages between environmental exposure to [.sup.210]Po and human health effects were identified in a literature review.

DISCUSSION: [.sup.210]Po accumulates in the ovaries where it kills primary oocytes at low doses. Because of its radiosensitivity and tendency to concentrate [.sup.210]Po, the ovary may be the critical organ in determining the lowest injurious dose for [.sup.210]Po. [.sup.210]Po also accumulates in the yolk sac of the embryo and in the fetal and placental tissues. Low-level exposure to [.sup.210]Po may have subtle, long-term biological effects because of its tropism towards reproductive and embryonic and fetal tissues where exposure to a single alpha particle may kill or damage critical cells. [.sup.210]Po is present in cigarettes and maternal smoking has several effects that appear consistent with the toxicology of [.sup.210]Po.

CONCLUSIONS: Much of the important biological and toxicological research on [.sup.210]Po is more than four decades old. New research is needed to evaluate environmental exposure to [.sup.210]Po and the biological effects of low-dose exposure to it so that public health offcials can develop appropriate mitigation measures where necessary.

KEY WORDS: cigarettes, drinking water, Fallon, human health, lead-210, leukemia, ovary, polonium-210. Environ Health Perspect 120:1230-1237 (2012). http://dx.doi.org/10.1289/ehp.1104607 [Online 26 April 2012]

In 2007, very high levels of the naturally occurring radioisotope polonium-210 ([.sup.210]Po) were discovered in drinking water from numerous private wells in Lahontan Valley, Churchill County, in northern Nevada. Of the 60 private wells and 3 public supply wells sampled in the valley (Seiler 2011), more than one-third of the private wells had [.sup.210]Po levels exceeding 0.55 Bq/L, and 10% had levels that exceeded 2 Bq/L. This level is extremely unusual--fewer than 100 wells in the United States have reported [.sup.210]Po activities that exceed 0.55 Bq/L, and the maximum value measured in Lahontan Valley, 6.59 Bq/L, is the fourth highest value reported in the United States (Seiler 2012).

[.sup.210]Po is one of the most toxic substances known because of its intense radioactivity, with 1 [micro]g of [.sup.210]Po having an activity of 1.66 x 108 Bq. After the death of Alexander Litvinenko from [.sup.210]Po poisoning in 2006, several papers were published that addressed the diagnosis, treatment, and toxicity of acute [.sup.210]Po poisoning (Harrison et al. 2007; Jefferson et al. 2009; Scott 2007) and the need for medical toxicology expertise about [.sup.210]Po because of its potential use in radiation terrorism events (Nemhauser 2010). The estimated acute lethal dose from oral ingestion for an adult if untreated is 10-30 [micro]g (Jefferson et al. 2009), and as little as 1 [micro]g might be lethal to the most radiosensitive members of the population (Scott 2007).

As an alpha-particle-emitting decay product of radium-226 ([.sup.226]Ra), [.sup.210]Po is classified as a Group 1 human carcinogen [International Agency for Research on Cancer (IARC) 2001]. Numerous epidemiological studies, which were reviewed by Canu et al. (2011), have investigated associations between exposure to members of the uranium-238 ([238.sup.]U) decay series in drinking water and cancers such as leukemia (e. …

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