Other Health Effects

FRAME 4.3 UNITS FOR MEASURING RADIATION AND EXPOSURE OF THE PUBLIC 

We are immersed in background radiation from natural and artificial sources, as seen in Table 4.6. Exposure to radiation can be from an external source irradiating the whole body or given organs or tissues resulting in an external radiation dose. Internally deposited radioactive material may cause an internal radiation dose that is usually focused on a specific organ or tissue. 

In the old system of units, exposure was described as radiation absorbed dose rad), dose equivalent (rem), roentgen (R), or Curie (Ci). The official system of measurement, the International System of Units (SI), uses the Gray (Gy) and Sievert (Sv), where 1 Gy = 100 rad and 1 Sv = 100 rem. 1 Gy corresponds to 1 J of energy deposition in 1 kg of material. It should be noted that the Gray (and rad) are purely physical quantities reflecting the amount of absorbed radiation, while the Sievert (and rem) reflects the biological effect of the absorbed radiation and depends on the radiation type and energy. 

the Gray expresses the amount of radiation absorbed by the body and the Sievert takes into account the effect of the radiation on the human body. For electromagnetic radiation (gamma and x-rays), these are considered as equal, that is, a dose of 1 Gy is equivalent to 1 Sv. However, for energetic particles absorbed by the body, the biological effects are more severe, so that a dose of one Gy of radiation by alpha particles would be equivalent to 20 Sv. 

The Becquerel (Bq) is defined as the number of disintegrations per second (dps) and is proportion to the older unit 1 Ci = 3.7 10 ° Bq. Radioactive transformation events are expressed in units of dps but because instruments are not 100% 

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For radiation doses <0.5 Sv, there is no clinically observable iacrease ia the number of cancers above those that occur naturally (57). There are two risk hypotheses the linear and the nonlinear. The former implies that as the radiation dose decreases, the risk of cancer goes down at roughly the same rate. The latter suggests that risk of cancer actually falls much faster as radiation exposure declines. Because risk of cancer and other health effects is quite low at low radiation doses, the iacidence of cancer cannot clearly be ascribed to occupational radiation exposure. Thus, the regulations have adopted the more conservative or restrictive approach, ie, the linear hypothesis. Whereas nuclear iadustry workers are allowed to receive up to 0.05 Sv/yr, the ALARA practices result ia much lower actual radiatioa exposure. 

Other health effects such as neuro-regulation (Butterfield et al, 2002, Bruni 1988), skin nutrition, thyroid regulatory function and regulation of blood pressure have also been reported with rice bran. However, more detailed studies are required to establish these results. 

Nieboer, E. and A. Yassi. 1988. Other health effects of chromium compounds. Pages 533-550 in J.O. Nriagu and E. Nieboer (eds.). Chromium in the Natural and Human Environments. John Wiley, NY. 

Chashschin, V.P., G.P. Artunina, and T. Norseth. 1994. Congenital defects, abortion and other health effects in nickel refinery workers. Sci. Total Environ. 148 287-291. 

Thorium is odorless and tasteless, so you cannot tell if you are being exposed to thorium. As shown in Tables 1 -1 through 1 -4, we know very little about specific exposure levels of thorium that result in harmful effects in people or animals. High levels of exposure have been shown to cause death in animals, but no direct cause of death could be determined and no other health effects have been reported. For more information, see Chapter 2. 

Some 3 billion have been spent on researching possible health effects from dioxin, and the results show that the risks were overstated. Last year, the Environmental Protection Agency s Science Advisory Board concluded that the evidence that dioxin is a cause of human cancer and other diseases is unconvincing.3 Furthermore, studies of workers exposed to the highest levels of dioxin ever experienced—levels that will never be seen again— have failed to produce any conclusive evidence of connections between dioxin and cancer4 and the other health effects.5... 

Until chemicals cause cancer accusations lost their capacity to excite the public, little attention was paid to the possibility that chemicals might cause other health effects, but such possibilities are now at center stage. I will not dwell on the chemicals cause... 

In the absence of evidence that environmental exposures are associated with cancer or other health effects, it would be reasonable to expect IOM committee members to have been skeptical about claims of such associations. Indeed, skepticism is the hallmark of science. The IOM committee veered far away from science. 

The IOM committee failed to read or heed its own conclusions about health risks from herbicides In contrast to TCDD [ dioxin, as used here], there is no convincing evidence in animals of, or mechanistic basis for, carcinogenicity or other health effects of any of the herbicides, although they have not been studied as extensively as TCDD. 23... 

One study, which investigated skin and anaphylactic reactions of guinea pigs sensitized by inhalation of tetryl smoke (Gell 1944), is discussed below. No other health effects were studied in animals. 

In addition to the aforementioned health effects, other health effects may occur in infants due to exposure of the embryo or foetus to radiation. These effects include a greater likelihood of leukaemia and, for exposure above various threshold dose values during certain periods of pregnancy, severe mental retardation and congenital malformations. 

Sakurai H (2000) Carcinogenicity and other health effects of acrylonitrile with reference to occupational exposure limit. Industrial Health 38(2) 165-180. 

In a reproductive toxicity study, a diet containing a number of heavy metals including the lanthanides (as oxides) was fed to mice over three generations. The highest calculated lanthanide dose in the diet was a combination of the following 156 mg dysprosium kg day , 5 mg europium kg day , 52 mg lanthanum kg day , 104 mg samarium kg day , 156 mg terbium kg day , 16 mg ytterbium kg day , and 10 mg thulium kg day . After three generations of exposure no reproductive or other health effects were observed in the treated animals. 

In ar r experimental or epidemiological data, there is also some imcertainly on whether the measured effects represent the tine most sensitive or critical effects. Neurodevelopmental effects are the most extensively studied sensitive end point for MeHg exposme, but there remains some imcertainty about the possibility of other health effects at low levels of ejqiosure. In particular, there are indications of immime and cardiovascular effects, as well as nemological effects emerging later in life, that have not been adequately studied. 

The Royal Commission on Environmental Pollution reported in 1996 that it was not aware of any study that provided firm evidence of adverse effects of contaminated land on health.10 However, the potential for health effects is real. Exposure to chemicals is a risk factor for several diseases and the International Agency for Research on Cancer has classified over 70 chemicals as human carcinogens, 60 as probable and more than 200 as possible carcinogens.11 There is evidence of an environmental influence in human diseases such as cancer,12 including geographic variation in cancer incidence in migrant populations, occupational studies and animal experiments. A number of studies also appear to suggest an association between other health effects and exposure to environmental chemicals. There are thousands of sites contaminated with hazardous chemicals with the potential to expose human populations. In the USA, the ATSDR has estimated that 46 % of the assessed National Priority List sites represent an actual hazard to health.13... 

Due to seasonal use of these compounds, human exposure is often transient, lasting only 3-6 months per year for some occupationally-exposed groups (such as farmers and sprayers). Intermediate studies in humans and animals or evaluations of workers using these agents would contribute greatly to the database concerning systemic and other health effects. These studies might also aid in the identification of dose-response relationships for effects from exposures to these pesticides. 

From 1935 to 1978, workers world-wide were exposed during periodic explosions at trichlorophenol production facilities as well as during their daily production activities. Table II illustrates some major industrial accidents which yielded published reports of health effects. Table III lists some major health outcomes reported following exposures to products contaminated with 2,3,7,8-TCDD. The primary dermal effect of exposure is chloracne, a persistent form of acne caused by exposure to a number of chlorinated organic compounds. Chloracne occurred in some exposed persons in all accidents, as well as in children in Seveso (2-4). Chloracne appeared with and without other health effects and persisted in some persons up to 28 years after exposure (5-6). 

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