The effects of noise and heat on the efficiency of human performance of psychomotor tasks at variable difficulty levels were investigated. Twenty four young, healthy volunteers with normal hearing, randomly divided into 4 equal sized groups, were tested in a climatic chamber under 4 combinations of two environmental conditions made up of noise and heat, each at two levels : 70 dB (A) (quiet), 100 dB (A) (noise) : 28°C (comfortable), 35°C (heat). A statistically balanced procedure was followed. Three physiological variables were also recorded : Heart rate, blood pressure and body temperature. A 2 × 2 analysis of variance showed rise in the physiological variables by noise and heat respectively as well as by their interactions. Performances of the psychomotor tasks were affected differently by noise and heat depending on the difficulty levels of the tasks. The interaction of noise and heat entailed superior performance of the tasks of memory and search, two hand coordination and reaction time, at moderate difficulty levels, but no distinct interaction effect was observed on the performance of tweezer dexterity.
Exposure to aromatic hydrocarbon solvents during pregnancy has been reported to adversely affect human embryonic development. This exposure may be due to deliberate abuse or may occur in the workplace. Xylene and toluene are the most common solvents encountered in the workplace and toluene is a constituent of commonly abused substances. This study was performed in an endeavour to fulfil two requirements for proof of teratog-enicity of a substance, namely development of an animal model and demonstration of a dose-response relationship of teratogenicity. To fulfil these aims, the possible teratogenic and embryotoxic effects of xylene and toluene on rat embryos during the organogenic period was investigated in vitro. Rat embryos were explanted on day 9.5 of gestation and cultured in heat-inactivated rat serum to which xylene or toluene (0.1, 0.5 or 1.0 μL/mL) had been added, dispersed in 0.1% DMSO. The amount of solvent in the culture medium was quantitated using gas chromatography. Neither xylene nor toluene had any observable teratogenic effect on the embryos in terms of increased malformations. However, both solvents were embryotoxic and caused a dose-dependent retardation of growth and develop-ment. A no-effect level was not established for either xylene or toluene, however, the lowest levels used for each of these compounds caused only a slight retardation of growth. Although there was no indication that exposure to these solvents caused a teratogenic effect, there was clear evidence of embryotoxicity. The embryotoxic levels of these solvents needed in culturewere higher than blood levels likely to occur in the human following industrial eposure or recreational abuse.
To determine cell-mediated immunity to nickel, another matrix in hard metal besides cobalt, lymphocyte transformation tests (LTT) with nickel were carried out in seven hard metal asthma patients all of who had reacted to cobalt chloride in the bronchial provocation tests (BPT). Immunoallergic studies prior to the present study revealed that threee of the seven generated a simultaneous positive reaction in the BPT with nickel and the allergosorbent test with nickel-conjugated human serum albumin (Ni-HSA). A stimula-tion index in LTT indicating a positive response was defined on the basis of results from the studies in the controls. Data revealed that two of the three who showed a combination of positive bronchial and immunological reactions with nickel had a positive LTT with nickel. In the other five, peripheral lymphocytes did not proliferate in response to nickel. Thus it is suggested that cell-mediated immunity to nickel as well as cobalt is implicated in some cases associated with hard metal asthma.