Cambridge Environmental has been acquired by CDM Smith, a full-service consulting, engineering, and operations firm providing solutions in water, environment, transportation, energy, and facilities to public and private clients worldwide. Press Release
Dr. Stephen Zemba is once again teaching the Air Pollution Control course in the Civil and Environmental Engineering Department at Tufts University. Dr. Zemba has been an adjunct faculty member at Tufts since 1995.
Cambridge Environmental recently evaluated whether polychlorinated biphenyls (PCBs) detected in the air in a Child Care Center would be harmful to infants and others. The measured concentrations exceeded U.S. EPA’s guidelines for allowable concentrations of PCBs in air in schools, but were, in our toxicologic judgment, acceptably small. Nonetheless, we recommended that the building be systematically surveyed, in hopes of finding important PCB-sources, and then of determining what remediation, if any, would be beneficial.
A redacted version of our letter-report is available here.
Cambridge Environmental recently evaluated whether polychlorinated biphenyls (PCBs) detected in floor boards, a concrete slab, and soil beneath a building would have harmed the health of workers’ engaged in demolition and renovation of the building. We estimated the concentrations of PCBs likely to have been in air inhaled by workers sawing the PCB-contaminated floor boards. We then evaluated the applicable toxicological literature and derived an acceptable level of PCB exposure that was more health protective than limits established by the Occupational Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH). We documented our findings in a letter report to our client.
A redacted version of Cambridge Environmental’s letter report is available here.
Drs. Stephen G. Zemba and Laura C. Green of Cambridge Environmental recently published a paper entitled, “Polychlorinated dibenzo(p)dioxin and furan (PCDD/F) congener profiles in cement kiln emissions and impacts.” This study examined the patterns of dioxin emissions in stack-tests at two Portland cement kilns that use a variety of fuels, including petroleum coke, coal, various supplemental fuels, and refinery distillation ends. All of the kiln emission profiles were found to differ markedly from profiles in ambient air. However, the small absolute dioxin emission rates from the kilns suggested that kiln impacts would not be detectable via ambient air monitoring, even in rural settings.
Hydrogen sulfide gas (H2S) has an obnoxious odor at very low concentrations and is thus responsible for considerable annoyance and concern in communities near H2S sources such as wastewater treatment plants. Human health data, however, do not clearly indicate that ambient concentrations (less than 1 ppm) are hazardous. Several regulatory or scientific organizations have derived standards or guidelines for H2S exposure for different populations, and these values vary considerably. Cambridge Environmental has examined some of the reasons for the differences, and suggests that community exposures may best be evaluated in light of the acute minimal risk level of 70 ppb derived by the Agency for Toxic Substances and Disease Registry (ATSDR).
The full text of Cambridge Environmental’s analysis is available here.
Dr. Edmund Crouch is participating on the National Academy of Sciences Committee “Long-term Health Consequences of Exposure to Burn Pits in Iraq and Afghanistan.” The committee is evaluating the long term health effects of exposure to burn pits in Iraq and Afghanistan. The committee anticipates releasing a report in mid-2011. More information is available here.
This semester, Dr. Stephen Zemba is teaching the course Air Pollution Control at Tufts University. This is the twelfth course that he has taught as Adjunct Professor at Tufts.
EPA awarded a contract to Cambridge Environmental entitled “Technical Support for the Assessment of Ecological Effects, Fate and Transport of Pesticides in the Environment.” The contract, valued at $11 million over 5 years, was awarded on February 1, 2011. Cambridge Environmental will support EPA’s Office of Pesticide Programs in the review and evaluation of studies submitted to EPA in pesticide registration applications.
Cambridge Environmental studies health risks from the presence of polychlorinated biphenyls (PCBs) in schoolsJanuary 25th, 2011
Cambridge Environmental scientists and engineers are studying risks of indoor air exposure to polychlorinated biphenyls (PCBs) in schools on the health of students and employees. The fact that most people’s exposures to PCBs stem primarily from what we eat, not what we breathe, has traditionally minimized concern about the latter exposures.
More recently, however, the detection of PCBs in indoor air in schools in Massachusetts, New York, and elsewhere in the U.S. and Europe has caused anxiety in parents and others, and cities and towns are grappling with the substantial costs of addressing these concerns.
The U.S. EPA and others have begun to respond to the health risks posed by this manner of PCB exposure. The Agency’s preliminary response has been to assess safety by comparing indoor-air PCB exposures to its “reference dose” (RfD); essentially, an acceptable daily intake for PCBs as a mixture. This reference dose was derived from laboratory-animal tests on a complex mixture of scores of PCBs, in particular, in a former commercial product known as Aroclor 1254. Importantly, however, the specific patterns of PCB congeners in indoor air in schools and homes differ markedly from those which comprise Aroclor 1254. For example, one of the PCB congeners that is prominent in indoor air, but not in Aroclor 1254, is 2, 4, 4’-trichlorobiphenyl (PCB 28). This congener is relatively nontoxic. Studies of people living in homes constructed with PCBs-containing caulking and other building-sealants reveal increased body-burdens of PCB 28 and several other PCBs, but current assessment methods do not provide a reliable method for characterizing the risks from these exposures. New methods are urgently needed.
To address this need, we at Cambridge Environmental have begun in-depth reviews of the physical, chemical, biological, physiological, and established or inferred toxicologic properties of each PCB congener of interest. Working with other scientists in the field, our primary goal is to develop new RfDs (or other metrics) that could be used to assess the potential hazards and risks associated with the PCBs found in air. Our hope is that these new, realistic metrics will assist school boards, environmental officials, and other community groups in understanding and addressing these issues.