Household Pesticides
The first Focus article reports the use of 4 billion household pesticide applications per year. Although allergies to insect parts, toxins, and vector-borne diseases are valid reasons to reduce infestations, potential adverse health effects of household pesticides pose special risks for children and the elderly. More studies on the potential chronic toxicity of pesticides are needed, but in the meantime, simple improvements in warning labels could help to reduce accidental poisonings.
Diet and Cancer
Scientists and the public share a gut feeling that proper diets may reduce cancer. Although the second Focus article supports this hypothesis, proof is wanting. The best information is derived from animal studies, which have repeatedly shown that reduction in caloric intake reduces the incidence of tumors. Multimillion-dollar studies are underway in an attempt to explain the mechanisms involved between certain foods and cancer, with hopes that dietary regimens can some day be used to reduce the incidence of cancer.
Sugar for Benzene
Techniques for replacing benzene with glucose for production of commercial chemicals has been accomplished using genetic engineering with microbes. The Innovationsarticle offers promise that instead of using an non-renewable resource like petroleum to synthesize benzene, fields of trees or plains of grasses could supply glucose as raw material and eliminate dangerous by-products from benzene chemistry in the bargain.
Fungicides and Human Health
Occupational exposure to the common class of fungicides known as the dithiocarbamates occurs in various industries and in farming. Parent ethylenebisdithiocarbamate compounds are toxic, as is the metabolite ethylenethiourea. Chronic human exposure leads to risks for carcinogenesis, as proven in animal studies. Houeto et al. urge that further human studies are necessary to quantitate these risks, but that regular surveillance of humans exposed to dithiocarbamates be initiated now, with particular attention to thyroid and liver toxicity.
Estrogen Receptors
Phytoestrogens are plant-derived compounds like the isoflavonoid coumestrol which bind to estrogen receptors and exhibit estrogenic activity in vivo. Markaverich et al. showed that coumestrol was an atypical phytoestrogen because even though it increased the mass of the uterus, it failed to stimulate cellular DNA synthesis and proliferation in immature female rats whose ovaries had been removed. These data raise the possibility that environmental phytoestrogens may act differently in premenopausal and post-menopausal women, and also indicate an incomplete understanding for the proposed procarcinogenic or anticarcinogenic effects of compounds like coumesterol.
Estogenicity of Phthalates
Jobling et al. found that 10 of 20 chemicals present in sewage were weakly estrogenic, as judged by estrogen receptor binding, proliferation of breast cancer cells, or stimulation of an estrogen-responsive reporter gene. The data suggest that contaminants such as phthalate esters could exert cumulative effects with other natural estrogenic compounds and enhance potential adverse effects on fertility or estrogen-related carcinogenicity.
Prenatal BaP + Lead Affects Fertility
The effects of potential chemical synergism on fertility were examined in an animal model. Kristensen et al. exposed pregnant mice to subtoxic lead concentrations or to lead plus benzo[a]pyrene to determine the degree of interaction between these chemicals. Data collected from six-month continuous breeding trials of their offspring demonstrated that the combination of chemical exposure reduced almost all indicators of ovarian development and fertility compared to those observed in mice exposed to BaP alone. Lead concentrations ranged between 2.44 and 5.26 µM/L in the exposed groups. There are no equivalent human data to gauge the possible detrimental effects of multiple chemical exposure.
Pregnancy and Trihalomethanes
Savitz et al. evaluated the reproductive health consequences of human exposure to chlorinated chemicals in the drinking water. Records from North Carolina on miscarriages, preterm deliveries, and low birth weights were used to assess risks associated with water source, amount, and trihalomethane concentration. There was no clear association between chlorination by-products and adverse pregnancy outcome.
Mortality in the Butadiene Industry
Mortality among 374 men working in rubber plants exposed to 1,3-butadiene revealed significantly elevated standardized mortality ratios for lymphosarcoma and reticulosarcoma based on 4 observed cases. Ward et al. examined records from plants where butadiene was a primary product and neither benzene nor ethylene oxide was present. An excess of these tumor types was also observed in the only other cohort of butadiene production workers previously studied. These data add to the weight of evidence for carcinogenicity of 1,3-butadiene in humans.
Mercury Exposure from Eating Seabass
Knobeloch et al. present a case study of a Wisconsin family who exhibited blood mercury levels 6- to 10-fold above normal. No sources of exposure were present; mercury came from a constant diet of fish. A variety of fish were eaten, but only seabass contained 0.5-0.7 mg/kg mercury; consumption estimates suggested the family consumed an average daily mercury intake of 0.5-0.8 µg/kg per week. Avoiding seabass consumption for 6 months resulted in blood mercury concentrations dropping to normal in the parents (3-5 µg/L), and sequential blood samples confirmed that half of the mercury was eliminated within 60 days.
Xenoestrogens in Food Cans
Brotons et al. report that extracts from canned foods or packing water exhibited some estrogenic activity in an MCF7 proliferative cell E-screen test. The lacquer-coated food cans were purchased in supermarkets from Spain and the United States. Some of the cans were packed in Brazil, France, and Turkey. Bisphenol A leached from the lacquer coating was identified by mass spectrometry as the contaminant with estrogenic activity in the canned food and water.