The 1984 Association Lecture of the Hospital Physicists' Association. Man and his environment.

Man has multiplied and become civilised by changing his environment to suit himself, especially by the development of agriculture. The near-elimination of infectious diseases among the young and middle-aged has increased the cancer death rates in Britain, which mainly affect the elderly, to 130 000 a year. A large proportion of cancers are initiated by environmental factors which should be discoverable and removable. Natural radon may be responsible for up to 400 cancer deaths annually and radiation from the nuclear industry for one or two more. An important number of cancers must be due to air pollution from the burning of coal and oil, which are also injuring the wildlife of the northern hemisphere and which, by increasing the concentration of carbon dioxide in the air, may be changing the climate of the whole planet.

Whole body cellular and collagen nitrogen in healthy and wasted man.

The classical literature shows that wasting of body protein takes place mainly from the cellular compartment leaving high proportions of extracellular collagen. Whole body nitrogen ( WBN ) is proportional to whole body protein (cellular + extracellular) while whole body potassium ( WBK ) is almost entirely intracellular. WBK might be an adequate index of cellular wasting. WBN was measured by neutron activation and WBK by counting 40K in 29 healthy males and 131 male and female patients with wide ranges of body composition. Our wasted patients with Crohn's disease or ulcerative colitis, had higher WBN / WBK ratios than matched healthy controls and the difference between the two groups was in the cellular ratio (23.6 mol of N/mol of K, 0.33 g of N/mmol of K, 3 mmol of K/g of N). A multiple regression model for all the subjects represented cellular nitrogen by a term in WBK and extracellular nitrogen by simple anthropometric measurements. The partial regression coefficient of WBN on WBK was 22.6 +/- 1.1 (SE) mol of N/mol of K; this was also similar to the cellular ratio. Our results were compatible with extracellular protein (mainly collagen, which is 35% of normal whole body protein) remaining resistant to wasting even when severe loss of cellular protein occurs. The high ratios of WBN / WBK in wasted patients can be explained by this disproportionate wasting of cellular substances and they do not imply alterations in the cellular N/K ratio. We suggested that the stable ratio of WBK to cellular protein makes it an effective index of cellular wasting. The resistance of collagen to wasting and the preponderance of extracellular mass in the fat-free mass of wasted subjects, make WBN and fat-free mass unreliable guides to the extent of wasting.

The indoor concentration of radon daughters in three different areas of the U.K.

The concentrations of radon daughters were measured in 86 rooms in three different areas in U.K.: Birmingham, Aberdeen and mainland Orkneys. The geometrical means of the concentrations in these areas were found to be 2.0, 6.7, and 2.5 mWL, respectively. In many cases, the ground beneath the houses was an important source of radon; where there was good sub-floor ventilation, the ground contribution was not important.

Effect of internal wall covers on radon emanation inside houses.

Most types of paint for the internal walls of houses will reduce radon emanation from building materials. At the same time, the effect of paint will increase the concentration of radon inside the material itself and will increase the radon emanation from unpainted areas. One type of wall paper contains 6 and 0.3 ppm of uranium in its decorated and undecorated surfaces, respectively, the colouring being the main source of uranium. Other wallpapers appear to be free from uranium. Wallpaper, gypsum and plaster may increase the radon activity inside houses depending on their radium contents.

A study of radon emitted from building materials using plastic alpha-track detectors.

Films made from cellulose nitrate LR-115 (Pathé Kodak) and CR-39 have been used for long-term measurements of the radon-222 emanation from building materials and the resultant activity inside houses. The emanation from crushed granite bricks is found to be produced from within the brick while in the clay bricks it originates in the surface layers only. The airborne radon activity inside houses constructed from clay brick is found on average to be 22 mBq 1-1 (0.57 pCi 1-1) while inside a closed vessel sealed to the brick the average equilibrium activity is 40 mBq 1-1 pCi 1-1).

The distribution of lead in human teeth, using charged particle activation analysis.

A technique has been developed to measure lead content in teeth using 3He2+ activation analysis. The alpha-activity produced in the teeth is recorded on plastic film alpha-track detectors (LR-115) and compared to the activity produced by the lead contained in standard glass. The concentration in teeth from three areas of the United Kingdom has been determined as a function of age. The lead content is found to increase with age in dentine and pulpal dentine, but not in enamel.