Is exposure to formaldehyde in air causally associated with leukemia?—A hypothesis-based weight-of-evidence analysis

Recent scientific debate has focused on the potential for inhaled formaldehyde to cause lymphohematopoietic cancers, particularly leukemias, in humans. The concern stems from certain epidemiology studies reporting an association, although particulars of endpoints and dosimetry are inconsistent across studies and several other studies show no such effects. Animal studies generally report neither hematotoxicity nor leukemia associated with formaldehyde inhalation, and hematotoxicity studies in humans are inconsistent. Formaldehyde's reactivity has been thought to preclude systemic exposure following inhalation, and its apparent inability to reach and affect the target tissues attacked by known leukemogens has, heretofore, led to skepticism regarding its potential to cause human lymphohematopoietic cancers. Recently, however, potential modes of action for formaldehyde leukemogenesis have been hypothesized, and it has been suggested that formaldehyde be identified as a known human leukemogen. In this article, we apply our hypothesis-based weight-of-evidence (HBWoE) approach to evaluate the large body of evidence regarding formaldehyde and leukemogenesis, attending to how human, animal, and mode-of-action results inform one another. We trace the logic of inference within and across all studies, and articulate how one could account for the suite of available observations under the various proposed hypotheses. Upon comparison of alternative proposals regarding what causal processes may have led to the array of observations as we see them, we conclude that the case fora causal association is weak and strains biological plausibility. Instead, apparent association between formaldehyde inhalation and leukemia in some human studies is better interpreted as due to chance or confounding

Effects of experimental lead exposure and the therapeutic effect of defatted Moringa oleifera seed meal on serum electrolytes levels of Wistar rats

The study was conducted to evaluate changes in serum electrolytes concentrations following experimental lead acetate (Pb) exposure and the effects of treatment with defatted Moringa oleifera seed meal (DMOSM) in wistar rats. Eighty adult wistar rats divided into 5 groups of 16 per group were used for this study. Rats in group I received only distilled water, group II were administered Pb solution orally at 480 mg/kg body weight, group III were co-administered Pb and DMOSM orally at 480 mg/kg respectively, group IV were pre-administered Pb orally at 480 mg/kg for the first two weeks and then administered DMOSM orally at 480 mg/kg for the subsequent two weeks, group V received DMOSM orally at 480 mg/kg. Four rats were sacrificed weekly from each group and blood samples for serum electrolyte analysis were obtained. Phytochemical screening of DMOSM revealed the presence of alkaloids, reducing sugars, cardiac glycosides and saponins. A significant decrease (P < 0.05) in the mean serum Ca2+ concentration in the rats in group III (1.52±0.17) was observed at week 3 compared to group IV (2.24±0.16). Mean serum concentration of PO4+ at week 1 in rats in group III (3.62±0.15) was significantly higher (P < 0.05) compared to group IV (2.89±0.18). Similarly, serum PO4+ level significantly rose at week 3 in group II (4.40±0.36) compared to rats in groups IV (2.61±0.11) and V (2.99±0.07) respectively. By week 4, the serum PO4+ concentration rose significantly in the rats in group III (5.47±0.11) compared to those in group I (3.27±0.24). Mean serum concentrations of sodium (Na+), chloride (Cl-), potassium (K+) and bicarbonate (HCO3-) were not significantly altered in all the test groups throughout the duration of the study. The result showed inability of DMOSM to mitigate Pb-induced alteration in serum Ca2+ and PO4+ levels in groups II and III.Keywords: Lead, Moringa oleifera, Phytochemical screening, Serum electrolytes, Wistar rat

Fernwaerme 1974 - 1990

SIGLEAvailable from TIB Hannover: F95B1909 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Bewertung epidemiologischer Untersuchungen ueber Dieselmotorabgas und Lungen- und Blasenkrebs Kritische Uebersicht

Cigarette smoking is the most important cause of lung and bladder cancer. A number of occupational carcinogens are also well known. The question whether general air pollution and specifically diesel exhaust emissions increase the risk of these two types of cancer is less certain. Diesel exhaust emissions have produced cancers experimentally in animals when administered in very high dosages, but the relevance of such experiments to man, exposed even under the worst conditions to very much lower dosages, is uncertain. The problems with regard to diesel exposures in man are first that we do not have any very good objective measurements of diesel exposures; second, that it is very difficult to allow adequately for the major risk factor of these two cancers, namely, cigarette smoking; and third, that there are powerful inducements towards biased ascertainment. Evidence is presented that smoking characteristics vary greatly in different occupations. Many studies of diesel (or suspected diesel) exposure in relation to lung and bladder cancer have not considered smoking at all. Those that have, have often considered only major differences in habits and ignored many other aspects of smoking, which may considerably increase carcinogenic risk. The main epidemiological studies considering diesel exhaust emissions in relation to lung and bladder cancer are critically reviewed. Our conclusion is that any increase in the risk of lung or bladder cancer from current exposures to diesel exhaust emissions cannot be large and may indeed not exist. Adequate allowance for other confounding factors has not yet been achieved. (orig.)SIGLEAvailable from TIB Hannover: RN 4481(112) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman