PubMed · 17180949
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Jennifer A Field, C Annette Johnson, Joan B Rose. 2006-12-01. What is "emerging"?. https://doi.org/10.1021/es062982z
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Simazine, first introduced in 1956, is a popular agricultural herbicide used to inhibit photosynthesis in broadleaf weeds and grasses. It is a member of the triazine family, and according to its physicochemical properties, it is slightly soluble in water, relatively nonvolatile, capable of partitioning into organic phases, and susceptible to photolysis. Sorption and desorption studies on its behavior in soils indicate that simazine does not appreciably sorb to minerals and has the potential to leach in clay and sandy soils. The presence of organic matter in soils contributes to simazine retention but delays its degradation. The primary sorptive mechanism of simazine to OM has been proposed to be via partitioning and/or by the interaction with functional groups of the sorbent. Farming practices directly influence the movement of simazine in soils as well. Tilled fields lower the runoff of simazine when compared to untilled fields, but tilling can also contribute to its movement into groundwater. Planting cover crops on untilled land can significantly reduce simazine runoff. Such practices are important because simazine and its byproducts have been detected in groundwater in The Netherlands, Denmark, and parts of the U.S. (California, North Carolina, Illinois, and Wisconsin) at significant concentrations. Concentrations have also been detected in surface waters around the U.S. and United Kingdom. Although the physicochemical properties of simazine do not support volatilization, residues have been found in the atmosphere and correlate with its application. Although at low concentrations, simazine has also been detected in precipitation in Pennsylvania (U.S.), Greece, and Paris (France). Abiotically, simazine can be oxidized to several degradation products. Although hydrolysis does not contribute to the dissipation of simazine, photolysis does. Microbial degradation is the primary means of simazine dissipation, but the process is relatively slow and kinetically controlled. Some bacteria and fungal species capable of utilizing simazine as a sole carbon and nitrogen source at a fast rate under laboratory conditions have been identified. Metabolism of simazine in higher organisms is via cytochrome P-450-mediated oxidation and glutathione conjugation.
Polybrominated diphenyl ether (PBDE) brominated flame retardants have recently been found to contaminate humans in the United States and other countries. U.S. human breast milk and blood levels of PBDEs are presently the highest in the world. U.S. cord blood samples tested positive for PBDEs, but until now there have been no peer-reviewed published data concerning levels of PBDEs in human tissue prior to and immediately after birth. Liver tissues were obtained from 4 stillborn fetuses and 7 liveborn infants, ranging from 20.5 to 39 wk gestational age; only 2 of the liveborn infants lived longer than 4 h and none were formula-fed or nursed, so tissue levels reflect intrauterine PBDE intake only. All samples were contaminated with PBDEs. Levels varied from 4 to 98 ppb, lipid. The mean level was 23.1 and the median 15.2 ppb, lipid. PBDE levels did not increase with gestational age. These data document the transfer of PBDEs from maternal to fetal tissue. PBDE concentrations are somewhat lower than those reported in adult blood or breast milk. The health consequences of prenatal contamination are not clear at present.
The major risks due to metal pollution of sediments consist of leaching to groundwater and potential toxicity to animals and/or plants. The objective of this study was to evaluate by means of an ecotoxicological approach the effects of the addition of cutting marble sludges on the mobile metal fraction of sediments polluted with heavy metals. The study was carried out on two sediments derived from mining activities in Portman Bay (SE, Spain) polluted by heavy metals. These sediments were mixed with sludges left after the cutting of marble. The results obtained by leaching experiments showed that the addition of marble cutting sludge, consisting mainly of carbonates, to a heavy-metal polluted sediment produces a decrease of available metal forms. The carbonate content seems to play a role in chemical stabilisation of metals and in a decrease of toxicity of sediments. The leached solutions have a non-toxic effect. The mild remediation by addition of sludge has moreover effects to long term.