Childhood leukaemia in Europe after Chernobyl: 5 year follow-up.

The European Childhood Leukaemia - Lymphoma Incidence Study (ECLIS) is designed to address concerns about a possible increase in the risk of cancer in Europe following the nuclear accident in Chernobyle in 1986. This paper reports results of surveillance of childhood leukaemia in cancer registry populations from 1980 up to the end of 1991. There was a slight increase in the incidence of childhood leukaemia in Europe during this period, but the overall geographical pattern of change bears no relation to estimated exposure to radiation resulting from the accident. We conclude that at this stage of follow-up any changes in incidence consequent upon the Chernobyl accident remain undetectable against the usual background rates. Our results are consistent with current estimates of the leukaemogenic risk of radiation exposure, which, outside the immediate vicinity of the accident, was small.

Human exposure to environmental polychlorinated dibenzo-p-dioxins and dibenzofurans: an exposure commitment assessment for 2,3,7,8-TCDD.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs and PCDFs) are released into the environment from the use of chemicals contaminated with PCDDs/PCDFs, the improper disposal of contaminated production wastes and incineration/other high-temperature processes. Certain congeners are extremely stable compounds which are persistent in the environment once released. An assessment is made of the sources of human exposure to one particular dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Representative values of 2,3,7,8-TCDD concentrations in the background environment and in man are selected from available data or, when not available, inferred from other relevant information. A pathway analysis is performed utilizing the exposure commitment method. Normal dietary intake of 2,3,7,8-TCDD is quite variable depending primarily on consumption of contaminated fish. Representative intake for the average adult of 0.1 ng day-1 may be associated with a human body burden of 100 ng (approximately 7 ng 2,3,7,8-TCDD kg-1 adipose tissue). The inferred biological half-time of this compound in the body is approximately 5 years. The exposure evaluation also accounts for secondary pathways to man of 2,3,7,8-TCDD in air and drinking water. Estimates of transfer factors obtained from the representative background levels should be generally relevant and may be applied to more specific cases of exposure.

Exposure of man to environmental hexachlorobenzene (HCB)--an exposure commitment assessment.

Hexachlorobenzene (HCB) is widely distributed and has high persistence in the environment. In the 1970s restrictions on its use as a fungicide for cereal grains were initiated, but there are other uses and releases from chemical manufacturing industries and waste disposal operations. Representative values for HCB in environmental media and in man have been used in an exposure commitment assessment. The human body burden of HCB, estimated at 0.7 mg, is derived mainly from dietary intake of fatty foods, diet contributing approximately 0.2 microgram day-1. Inhalation is estimated to contribute about two orders of magnitude less. The assessment indicates a low exposure to HCB from the general environment, but populations exposed to direct contamination have had increased intake via one or both pathways.

Exposure of man to environmental aluminium--an exposure commitment assessment.

Aluminium is one of the most abundant elements in the environment and is released from both natural and anthropogenic sources. Representative values of aluminium concentrations in the background environment and in man are selected from available data and a pathway analysis is performed utilising the exposure commitment method. Using a derived estimate of the body burden (60 mg), a representative value for dietary intake (20 mg day-1) and fractional absorption of 0.01, a mean retention time of A1 in the body of 300 days is obtained. This corresponds to a biological half-time of 210 days. The assessment indicates that an average dietary intake rate of 20 mg day-1 contributes 660 micrograms kg-1 of aluminium to the body, while inhalation of aluminium in air makes, in comparison, a negligible contribution to the body content.

Modeling exposure routes to man of trace metals associated with acid precipitation.

Pollutant metals released to the environment disperse and interact in various ways before arriving at sensitive receptors. Modeling of pollutant behavior may be by time-dependent or time-independent means. The time-independent, exposure commitment method requires a less extensive data base and can begin with general associations between environmental concentrations or fluxes. Such assessments for representative background conditions have been performed for most of the metals associated with acid precipitation. Examples are given here for cadmium and mercury. These overviews are only the beginning stage of relating pollutant releases to environmental effects.

Exposure of man to environmental copper--an exposure commitment assessment.

Copper, an essential element for man, is widespread in the environment and is released from both natural and anthropogenic sources. A summary of representative values of copper concentrations in environmental media is presented and a pathways analysis performed utilizing the exposure commitment method. The assessment indicates that an average dietary intake rate of 2 mg day-1 contributes 630 micrograms kg-1 of copper to the body, while inhalation of copper in air (0.05 micrograms m-3 in urban air and 0.02 micrograms m-3 in rural air) makes, in comparison, a negligible contribution to the body content.

Environmental nickel pathways to man.

From representative values of nickel concentrations in the background environment, a pathways analysis and exposure assessment for man is performed. Estimated daily intakes of nickel are of the order of 170 micrograms via ingestion and 0.4 microgram via inhalation. The ingestion pathway is thus quite predominant in normal circumstances. From the estimated body burden of nickel of 500 micrograms, the effective mean retention time of nickel in the body is inferred to be 200 days. The exposure evaluation is performed for total nickel in the environment and in man. Assessments for specific nickel compounds can be made as data become available.

Exposure of man to environmental selenium - an exposure commitment assessment.

Selenium is an element which occurs naturally in varying concentrations in soil and is released from industrial sources, particularly from fossil fuel combustion. Harmful effects in animals and man may result from both deficient or excessive amounts of intake. Representative values of selenium concentrations in the background environment and in man are selected from available data and a pathway analysis is performed utilizing the exposure commitment method. Dietary intake of selenium is of the order of 70 micrograms d-1. With fractional absorption of 80% and retention in the body of 90% for an effective retention time of 140 days, the estimated mean body content of selenium is 7 mg. The contribution to the body burden from inhalation intake is much less significant. The exposure evaluation is performed for total selenium in the environment and in man. The parameters may be adjusted for specific selenium compounds, if data are available, and for more particular environmental and exposure conditions as required.

Exposure of man to environmental PCBs--an exposure commitment assessment.

Polychlorinated biphenyls have been widely used in industry, but because of recognised environmental and human health hazards are now mostly restricted to closed electrical systems. PCBs are extremely stable compounds and are persistent in the environment once released. Representative values of PCB concentrations in the background environment and in man are selected from available data and a pathway analysis is performed utilizing the exposure commitment method. Dietary intake of PCBs is quite variable depending primarily on consumption of contaminated fish. Representative intake of 24 micrograms d -1 may be associated with concentrations in man of 0.35 mgkg -1 of body weight, from which a mean residence time in the body of 3 years may be inferred. Diminished intake and body concentrations should eventually become evident, reflecting reduced industrial usage and releases to the environment of PCBs. The exposure evaluation accounts also for secondary pathways to man from PCBs in air and drinking water. The analysis provides a framework for assessment of PCB movements through the environment in pathways to man. The estimates of transfer factors obtained from representative background levels should be generally relevant and may be applied to more specific cases of exposure.

Exposure of man to environmental nickel--an exposure commitment assessment.

Nickel is one of many trace metals that are pervasive in the environment, being released from natural and man-made sources, and to which man is exposed. Representative values of nickel concentrations in the background environment and in man are selected from available data and a pathway analysis is performed to illustrate application of the exposure commitment method to environmental pollutant assessment. Estimated dietary intake of nickel is of the order of 170 micrograms d-1. With fractional absorption of five per cent, retention in the body of 30 per cent of the absorbed amount and an estimated mean body content of nickel of 500 micrograms, an effective mean retention time of 200 days is derived. Contributions to the body burden from drinking water and inhalation of nickel in air are generally less important than dietary intake in normal circumstances. The exposure evaluation is performed for total nickel in the environment and in man. Relationships for specific nickel compounds would be useful and can be derived in a similar fashion as data become available.

The exposure commitment method with application to environmental mercury.

Exposure commitment is a measure of the concentration and duration of a pollutant in an environmental medium. It is the basis of a time-independent method of pollutant pathway analysis. Applied to environmental mercury, contributions to concentrations in the human body from inhalation and from ingestion of terrestrial and aquatic foods areevaluated.

Exposure of man to environmental arsenic - an exposure commitment assessment.

The Monitoring and Assessment Research Centre (MARC) has been developing and applying the exposure commitment method to the assessment of pollutant transport in the regional and global environment. Exposure commitments give a basis for comparing contributions to exposure from various pathways and for estimating equilibrium concentrations resulting from continuing releases. As an illustration of the method, environmental aspects of arsenic are summarised and relationships are formulated between environmental sources and concentrations of arsenic in the body. Arsenic is present in the environment primarily in inorganic form; however, relatively higher concentrations of arsenic in organic forms occur in fish. Ingestion intake by man is variable, dependent on seafood consumption and also on geography, determining for example the levels which may be present in drinking water. Based on measured absorption and retention of arsenic in man, it is estimated that an ingestion intake rate of arsenic in terrestrial foods of 1 mg y-1 contributes a concentration of arsenic in the body of 0.28 microgram kg-1. The relationship is 0.14 microgram kg-1 per mg y-1 intake of organic arsenic in seafood. The body burden of arsenic is estimated to be about 1 mg from reported tissue measurements and from representative intake estimates. Harmful effects from arsenic in the body could be expected at levels perhaps 5 to 80 times the current background levels. Uncertainties are recognized. Improved estimates of the transfer fractions can be made as additional data are acquired.

The exposure commitment method in environmental pollutant assessment.

The exposure commitment method is a time independent approach to pollutant assessment. The exposure commitment is a measure of the intensity and duration of a pollutant's presence in an environmental reservoir. The method is a particularly convenient means of comparing contributions to intake and exposure from various pathways and in expressing source-receptor relationships. The concepts and definitions of the method are presented and application shown for the transfer of lead and cadmium from general atmospheric sources to man.