Sustainability of Planet Earth
In order to maintain planet earth for all peoples, Cairns suggests the need for an approach that is radically different from the usual economic growth cure-all; sustainable development is required sooner lest the consequences lead to complete and irreversible collapse of ecosystems necessary for survival.
Autoimmunity and Bovine Spongiform Encephalopathy
Ebringer et al. analyzed molecular sequence databases and report that three bacteria share sequences with the encephalitogenic peptide of bovine myelin, and that three molecules in Escherichia coli show molecular mimicry with host encoded "prion" protein. The authors suggest that immunotoxic reponses to these bacteria may cause neurological tissue injury resembling BSE.
Research Redux
The NIEHS News takes a tour of the NTP archives in Research Triangle Park, North Carolina. As the repository for 30 years' worth of toxicological research, this little-known treasure offers a unique wealth of resources to investigators seeking to recreate earlier study findings or build on the current body of toxicology data.
The Sheltering Forest
The environmental and health effects of deforestation are examined in the Focus article. Worldwide, the rate of deforestation makes it difficult to accurately quantify and assess these effects, but emerging infectious diseases, dramatic climate changes, and heightened emissions of greenhouse gases are three good reasons why the consequences of deforestation must be taken seriously.
New Test Takes the Bite out of Cockroaches
Exterminating cockroaches is one thing but finding and cleaning up their microscopic antigens is another. Because even one picogram of cockroach antigen can trigger a potentially fatal allergic reaction in a sensitive asthmatic, it's crucial that asthma sufferers be able to remove the antigens from their homes. Scientists have devised a new test kit, described in the Innovations article, that allows the user to identify the precise location of antigens in the home for a complete cockroach cleanup.
Mouse Liver Tumors and Risk Assessment
A review of 138 mouse carcinogenicity studies conducted by the agrochemical industry indicates that 37 were positive for liver tumors in one or both sexes (Carmichael et al.). Only 1/8 chemicals positive in the Ames test was judged to be carcinogenic; 6/37 chemicals positive for carcinogenicity were genotoxic. There was a clear relationship between hepatomegaly at 1 year and positive tumorigenesis at 18 months or 2 years. The authors conclude from epidemiological evidence and from bioassay data that liver tumors in humans can be mostly associated with hepatitis and/or cirrhosis and not to natural or man-made chemicals.
Kinetics: From Rats to Humans
Predictions of metabolism of about 100 chemical compounds in humans based on data in rats was examined by Sarver et al.. The authors report that an allometric model which does not necessarily take into account lipid solubility was suitable for estimating chemical metabolism in humans using data from rats, with the exception of chemicals like TCDD that are extremely lipid soluble.
Phenolphthalein, Laxatives and Human Cancer
A potential association between laxatives and colon cancer was examined by Longnecker et al. in three studies with 730 cases and 907 controls. There did not appear to be an increased risk for phenolphthalein-containing laxatives to cause adenomatous colorectal polyps. However, less than 5% of the subjects used laxatives frequently and the confidence intervals were relatively wide, so no definitive answer was posssible.
Pesticides and Children's Brain Tumors
Risk of household pesticide exposure for brain tumors in children of women from pregnancy to diagnosis was studied by Pogoda and Preston-Martin in Los Angeles County, California. Risk was significantly elevated for prenatal exposure to flea-tick pesticides, particularly among subjects less than 5 years old at diagnosis; prenatal risk was highest for mothers who prepared, applied, or cleaned up flea/tick products themselves. A significant trend of increased risk with increased exposure was observed for number of pets treated. Sprays or foggers were the only products significantly related to risk; further research was suggested to identify specific chemicals involved.
Herbicides and Breast Cancer
An ecologic study of Kentucky counties was conducted by Kettles et al. to examine the potential association between exposure to triazine herbicides and the incidences of breast cancer rates. There was a statistically significant increase in breast cancer risk with medium and high levels of triazine exposure, based on estimates of contaminant exposure and state registry data for tumors.
Reanalysis: Declining Sperm Density Worldwide?
A reanalysis of the 61 Carlsen studies that reported a worldwide decline in sperm density was conducted by Swan et al. using multivariate linear and non-linear models. A decline in sperm density was seen in the United States. and Europe but not in non-Western countries, supporting Carlsen's findings, but the cause(s) of intraregional and temporal differences warrant further study.
Particle Composition Determines Human Inhalant Responses
Six volunteers were exposed to ultrafine magnesium oxide particles for 15-45 min to attain cumulative exposure concentrations from 261 to 6435 mg 
min/m3 (Kuschner et al.). Bronchoalveolar lavage cell and cytokine concentrations, pulmonary function, and peripheral blood neutrophils were quantified 18-20 hr after inhalation. There were no significant changes in marked contrast with the known pulmonary inflammatory responses following zinc oxide particle inhalation, supporting the concept that particle chemical composition, in addition to particle size, is an important determinant of inhalant responses.
Estrogenicity of PCBs and Metabolites
Fielden et al. used a battery of in vitro and in vivo assays to investigate the estrogenic and antiestrogenic activities of the pentachlorobiphenyl PCB104 and its p-hydroxylated and p-chlorinated derivatives. The studies demonstrated that in addition to the metabolites, selected parent PCB congeners may also exhibit estrogenic and antiestrogenic activities.
PCBs and Pesticides in Human Breast Milk
Breast milk taken from 92 Kazakstan donors was examined for organochlorine pesticides, PCBs, PCDDs, and PCDFs by Hooper et al.. The most prevalent residues were DDE and DDT, hexachlorocyclohexane, and hexachlorobenzene, with ß-hexachlorocyclohexane among the highest levels reported in the published literature. PCB-TEQ levels were similar to those reported in industrialized European countries.
