The use of neutron and charged particle induced reactions is briefly discussed and the experimental facilities employed in this work are described. The qualitative elemental composition of human lung tissues, taken from individuals deceased from non-lung-related causes, was determined by prompt gamma-ray neutron activation analysis (PGNAA), cyclic neutron activation analysis (CNAA), conventional neutron activation and proton induced X-ray emission analyses. In addition elemental concentrations were determined by CNAA and conventional activation. Concentration values for elements previously not extensively reported in the literature, Ce, Cl, F, Hf and Sc were obtained as well as values for 18 other elements. Fingernail samples were investigated in order to study the uptake of Se and Zn supplementation. The effect of the rate of excretion through fingernails of Se and Zn on the level of Na is described. The variations in the elemental concentrations from finger to finger are shown for Se, Cl, Na and K and the variations from hand to hand, of a control, are shown for Br, Cl, K, Mg, Na, Rb, S, Se and Zn. Concentration values for Br, Ce, S, and Se, for which values available in the literature are very few , are presented. Bone biopsy samples were collected from the iliac crest of subjects, divided into four groups depending on the length of dialysis treatment, aluminium levels in blood and bone pathology in terms of osteoporosis. Fluorine concentration in the samples were determined by CNAA and proton Induced gamma-ray emission (PIGE) in conjunction with Rutherford backscattering (RBS). The relation between the A1 levels in the system and the F concentrations in the bone samples was investigated and the existence of a positive correlation between A1 and F was found. The effect of mass fractionation was tested for small and large sample fractions of Bowen's kale and the detection sensitivities were determined in counts/mg of sample. The concept of the sampling factor in CNAA was established for the comparative determination of elemental concentrations and the representative mass of Bowen's kale required for the determination of Br, Ca, Cl, K, Mg, Na, Rb, S, Se, Sm and V were found. Following the Chernobyl reactor accident, measurements of University of Surrey students returning from Kiev and Minsk were conducted for the neck region and the chest region. The activity of iodine (I-131) in the thyroid and the effective dose equivalent were calculated. The activities in the chest region for Cs-137, Zr-95 and the annihilation radiation were determined using a chest water-phantom. Measurement of radioactive particulates in air filters, collected from air ventilation units in the London area, a month after the radioactive cloud from Chernobyl had passed over the U.K., was carried out and the concentrations of 17 fission products in the atmosphere were calculated.