Up close and personal When it comes to measuring human exposure to toxic pollutants ambient environmental (area) monitoring appears to give misleading results according to a growing number of scientists. Instead what is needed is a greater use of personal monitors that measure how much contamination actually comes into contact with individuals. In 1987 the US EPA published the results of a detailed six-year study that involved hundreds of people. The Total Exposure Assessment Methodology (TEAM) study approach combined probability sampling with direct measurements of human exposure.1 TEAM measured peoples' exposure to pollutants in the air using small portable personal exposure monitors. The monitors consist of a pump and Ælter system which records the contaminants to which the wearer is exposed.The study also measured contaminant levels in their drinking water and in their breath. For exposure the results were remarkably consistent. Personal air exposures to every one of the eighteen target volatile organic compounds (VOCs) including benzene and chloroform were far greater than mean outdoor concentrations–2 to 5 times greater than concurrent outdoor measurements. These studies took place in areas of intensive chemical Fig. 1 Exposure to toxic pollutants. 16N J. Environ. Monit. 2000 2 This journal is # The Royal Society of Chemistry 2000 manufacturing and petroleum reÆning Elizabeth NJ Bayonne NJ Los Angeles CA Antioch CA and Pittsburg CA. Since that time personal monitoring studies have substantiated these results and revealed that human exposure is signiÆcantly greater than outdoor air monitoring would suggest for many other pollutants including carbon monoxide pesticides lead and Æne particulates studies.2 The main reason for this disparity is that people spend most of their time indoors where pollution levels are higher and sources are different.For example in the US cars and industry are the main sources of benzene emissions. But for personal exposures the numbers are very different smoking and second-hand smoke accounts for 45 percent and driving and other personal activities account for 32 percent. Cars account for 20 percent and industry contributes just three percent.Yet funding for research on indoor air pollution and personal monitoring is just one tenth of that for outdoor air research (Fig. 1).3 For the reasons outlined over 200 scientists who work in the Æeld of human exposure and risk assessment have endorsed this statement ``Human personal exposure needs to receive greater emphasis in the nation's programs of environmental regulation research monitoring and public education.'' International leaders in the Æelds of epidemiology and exposure research have also signed what has come to be known as the consensus statement which was launched at the 1998 joint annual meeting of the International Society for Exposure Analysis (ISEA) and the International Society of Environmental Epidemiology (ISEE) in Boston MA.Watching the detectives The point of personal human exposure monitoring is to determine pollutant concentration levels that actually come into contact with the human body according to Wayne Ott an exposure scientist. While at the EPA he managed research on air pollution toxic substances and human exposure.4,5 Ott US Focus offers an analogy to contrast the personal exposure assessment approach with more traditional technologies used in environmental monitoring.4 The analogy starts with a typical murder mystery story starring Hercule Poirot or Sherlock Holmes. These detectives start with the victim and then work backwards to Ænd the source of the crime. If the victim was shot Poirot might analyze bullet fragments sample the victim's body and look for Ængerprints.They look for facts surrounding the Æring of the gun– which in the analogy is equivalent to the emission of a pollutant from its source. This sort of ``working backwards'' is what personal exposure monitoring is about according to Ott who is now based at Stanford University in Palo Alto CA. He describes Poirot Holmes and personal exposure assessors like himself as ``receptor-oriented.'' In contrast traditional monitoring approaches which are enshrined in environmental regulations proceed in the opposite direction–they are ``source-oriented'' not ``receptororiented'' according to Ott. If Sherlock Holmes were to proceed with a sourceoriented approach he would Ærst discover a gun and its spent shells.He would know that the gun had been Æred but not where the bullets had gone nor whether they had injured anyone. Holmes would have to start at the source and then try to work forward to follow the bullets. There has never been a murder mystery like it and there never will be Ott says because the approach does not work. Yet most current environmental laws are concerned with emissions or with efØuents–with the bullets. They do not for example begin with people and attempt to see whether these pollutants actually are reaching any members of the general public. These laws were written when outdoor pollution from leaking waste dumps dirty smokestacks and noxious discharges was obviously fouling the environment.But as source emissions have been reduced thanks to the success of these laws it becomes extremely important to determine whether pollutants are reaching people and by how much. Safe as houses? Although indoor air issues have received relatively little prominence they have a direct impact on peoples' lives particularly children according to John Roberts whose consultancy Engineering Plus in Seattle WA specializes in assessing and controlling dangerous pollutants in the home. For small children house dust is a major source of exposure to cadmium lead and other heavy metals as well as polychlorinated biphenyls and other persistent organic pollutants. This is because pollutant-laden particles are tracked in and deposited onto carpets which act as deep reservoirs.Once inside many compounds particularly pesticides are more persistent because they are protected from sunlight and bacterial degradation. A standard vacuum cleaner does not remove these toxic compounds nor does it get rid of other asthma-inducing allergens such as animal dander dust mites and mold.6 But despite this gloomy picture there are simple low-cost ways to lower exposure from dust and carpets. These include leaving shoes at the door using industrial welcome mats and vacuum cleaners which incorporate dust sensors. Most people however are unaware of the ubiquity of indoor air pollution or how to reduce it. An exception to this lack of information is an innovative program in Seattle WA.Trained volunteers in the Master Home Environmentalist Program (MHEP) provide free assessments to families who wish to reduce their exposure to indoor pollutants house dust and chemicals.7 Indoor pollution is also responsible for ``sick building syndrome'' a phenomenon which is still poorly understood. EPA has just Ænished a major study of large ofÆce buildings across the US. The Building Assessment Survey Evaluation (BASE) is the Ærst study to gather baseline information on ``normal'' buildings according to project manager John Girman in Washington D.C.8 Researchers are currently analyzing the data that include information on ventilation systems and ducts air Øows Æltration VOCs bacteria fungi Æne particles and the questions about the health of ofÆce workers.Girman hopes that his work will provide building managers with some guidance for reducing contaminant levels in ofÆce buildings–information which they do not have now he says. Despite a long list of recent US Government reports identifying indoor pollution as one of the most serious environmental risks to public health there is no government agency with a strong legislative mandate to address the problem.9 OfÆcials speculate that such a mandate is unlikely because many indoor spaces particularly dwellings are private not public places. From this point of view tackling indoor pollution is a personal choice. But personal choice Focus depends on access to information.For many aspects of indoor pollution such as baseline data about schools or sources in dwellings the information does not exist yet. Perhaps the situation will improve if policy makers heed exposure scientists' pleas. Notes 1 L. Wallace The Total Exposure Assessment Methodology Study Summary and Analysis Volume 1 United States Environmental Protection Agency OfÆce of Research and Development EPA/600/6-87/002a 1987. 2 A. P. Jones Atmos. Environ. 1999 33 4535. 3 J. M. Seltzer Occup. Med. 1995 10 26. 4 W. R. Ott J. Expos. Anal. Environ. Epidemiol. 1995 5 449. 5 W. R. Ott and J. W. Roberts Sci. Am. 1998 278 86. 6 Lewis et al. Arch. Environ. Contam. Toxicol. 1994 26 37. 7 J. W. Roberts and P. Dickey Rev. Environ. Contam. Toxicol. 1995 143 59. 8 General information about the BASE project is available at http:// www.epa.gov/iaq/base/index.html 9 Indoor Pollution Status of Federal Research Activities August 1999. United States General Accounting OfÆce Report GAO/RCED-99-254. Rebecca Renner Science writer and editor Tel z1 570 321 8640 Fax z1 570 321 9028 E-mail applepie@sunlink.net 17N J. Environ. Monit. 2000 2