Controlling lead concentrations in human blood by regulating the use of lead in gasoline

After having been emitted at maximum rates in the 1960s and 1970s, lead has become less ubiquitous in industrialized countries as a result of increasingly stringent policies to limit the use of this heavy metal as an anti-knock additive in gasoline. Using a detailed reconstruction of lead emissions in Europe (PbE), of the air concentration of lead in Europe (PbC) and repeated measurements of lead concentrations in human blood (PbB) in Germany since about 1980, we have constructed an empirical model that estimates PbB given PbE. This model is used for 2 purposes: i)To estimate PbB levels for the 1960s and 1970s in Germany, when emissions were maximum and monitoring blood levels had not yet begun. It turns out that PbB peak emissions were reaching a mean level, which health officials considered potentially harmful for fetuses and small children. ii) To estimate how PbB levels may have developed if regulations of the use of lead in gasoline had been implemented differently. In case of no or delayed regulations, the model estimates that PbB levels well beyond the critical level would have emerged. Thus, the regulation instituted in Germany since the 1970s has reduced significant health hazards.     

Masking of circadian activity rhythms in male golden hamsters by the presence of females

Summary Wheel-running activity was recorded in male golden hamsters (Mesocricetus auratus) that had been blinded by bilateral enucleation and then kept singly in cages in a continuously darkened cabinet (room 1). In an adjacent cabinet (room 2), sighted male and female hamsters were kept in a 12:12-h light-dark cycle. For time spans varying from 15 to 45 days, two females within their cages were transferred for 3 h each day from room 2 to room 1 at the same time of light-off in room 2. Afterwards, two sighted male hamsters were transferred to room 1 for 3 h each day for 28 days. For the last 70 days of the experiment, all blinded males were transferred permanently to room 2. There were three main results: (1) bilateral enucleation of the males in room 1 had no effect on phase or period of the free-running rhythm; (2) the rhythms of the blinded males were entrained neither by the 3-h daily presence of two females nor after the transfer into room 2; (3) the presence of females usually released activity in the males depending on the circadian phase at which the exposure to females occurred. The masking responses were maximal at the beginning of the activity time, and reached a minor second maximum approximately 9 to 12 h later.     

Comparison of intake of nicotine from environmental tobacco smoke between nose and mouth breathers

Two experiments were carried out in order to investigate nicotine intake through passive smoking. In the first study, carboxyhemoglobin (COHb) and serum cotinine were found to increase to a similar extent in seven subjects breathing through the nose only and in another seven subjects breathing through the mouth only during exposure to environmental tobacco smoke. Similarly, no significant difference was found in urinary excretion of nicotine and cotinine over a period of 72 hours, although nicotine and cotinine excretion tended to be slightly higher after inhalation through the nose only. In the second study, nicotine was measured in four subjects who held mainstream or sidestream smoke in the mouth without inhaling. Cotinine levels in serum and amounts of nicotine and cotinine excreted in the urine were low compared with those measured in the breathing study. Nicotine from sidestream smoke, however, is more effectively absorbed by the oral mucosa than nicotine from mainstream smoke. The data suggest that nicotine intake from passive smoking largely takes place in the bronchial tree and that nicotine absorption via the nasal or the oral mucosa is only of minor significance.