People detection

The results of human activities described in the previous sections of this chapter have resulted in the release of thousands of pollutants into the environment. In a good portion of the world, ground- and surface waters are treated to disinfect biological agents and remove chemical pollutants prior to human consumption. Despite such treatment, the water consumed by almost all of the world s population is contaminated with chemical toxicants. In the United States, tap water tests from 1998 through 2003 on more than 39,000 water systems in 42 states, serving more than 231 million people detected 260 different pollutants. These are characterized by their sources in Tables 8.2-8.6. The data that follow in these tables, as well as those in Table 8.7, were compiled and reported by the EWGJ64I... 

Odors are characterized by quaUty and intensity. Descriptive quaUties such as sour, sweet, pungent, fishy, and spicy are commonly used. Intensity is deterrnined by how much the concentration of the odoriferous substance exceeds its detection threshold (the concentration at which most people can detect an odor). Odor intensity is approximately proportional to the logarithm of the concentration. However, several factors affect the abiUty of an individual to detect an odor the sensitivity of a subject s olfactory system, the presence of other masking odors, and olfactory fatigue (ie, reduced olfactory sensitivity during continued exposure to the odorous substance). In addition, the average person s sensitivity to odor decreases with age. 

Consumer Products. Laser-based products have emerged from the laboratories and become familiar products used by many millions of people in everyday circumstances. Examples include the supermarket scaimer, the laser printer, and the compact disk. The supermarket scanner has become a familiar fixture at the point of sale in stores. The beam from a laser is scaimed across the bar-code marking that identifies a product, and the pattern of varying reflected light intensity is detected and interpreted by a computer to identify the product. Then the information is printed on the sales sHp. The use of the scanner can speed checkout from places like supermarkets. The scanners have usually been helium—neon lasers, but visible semiconductor lasers may take an impact in this appHcation. 

Saccharin imparts a sweetness that is pleasant at the onset but is followed by a lingering, bitter aftertaste. Sensitivity to this bitterness varies from person to person. At high concentration, however, most people can detect the rather unpleasant aftertaste. Saccharin is synergistic with other sweeteners of different chemical classes. For example, saccharin—cyclamate, saccharin—aspartame, saccharin—sucralose, and saccharin—aUtame combinations all exert synergy to various degrees. The blends, as a rule, exhibit less aftertaste than each of the component sweeteners by themselves. 

Detection. Many people can detect hydrogen cyanide by odor or taste sensation at the 1 ppm concentration in air, most at 5 ppm, but HCN does not have an offensive odor and a few people cannot smell it even at toxic levels. Anyone planning to work with hydrogen cyanide should be checked with a sniff test employing a known safe concentration. This test should be given periodically. Several chemical detection and warning methods can be employed. The most rehable are modem, electronic monitors based on electrolytes that react with hydrogen cyanide. 

Instrumentation (Arthur D. Little, Inc., and Levine, 1986.) Instrument systems are an essential part of the safe design and operation of systems for storing and handling highly toxic hazardous materials. They are key elements of systems to eliminate the threat of conditions that could result in loss of containment. They are also used for early detection of releases so that mitigating ac tion can be taken before these releases result in serious effects on people in the plant or in the public sector, or on the environment. 

The basic approach is to direct the system to the safest operating level relative to people or the environment when any emergency condition is detected, including power loss. An important concept of process control safety is to have adequate redundancy to reduce unwanted shutdowns and maintain an adequate level of certainty that a safe state will result if a real emergency does occur. As far as possible, instruments should be of the fail-safe type. 

In the Slimmer of 1989, Rutland Water, the largest man-made lake in Western Europe and which supplies potable water to approximately 500 000 people in the East of England, contained a heavy bloom of Microcystis aeruginosa. By the end of the summer, a number of sheep and dogs had died after drinking from the bloom and concentrated scum. Analysis revealed that the cyanobacterial bloom material was toxic to laboratory mice, and that rumen contents from a poisoned sheep contained fivemicrocystin variants.Microcystins were detected in waters used for recreation in Australia at concentrations greater than 1 mg per... 

You may believe that the accidents could not happen at your plant because you have systems to prevent them. Many of the accidents I describe occurred on plants that had such systems, but the systems were not always followed. The accidents happened because of various management failures failure to convince people that they should follow the systems, failure to detect previous violations (by audits, spot checks, or just keeping an open eye), or deliberately turning a blind eye to avoid conflict or to get a job done quickly. The first step down the road to many a serious accident occurred when someone turned a blind eye to a missing blind (see Chapter 1). 

An automatic control system is often introduced because it appears to do a job better than the human. However, the human is still asked to monitor its effectiveness. It is difficult to see how the worker can be expected to check in real time that the automatic control system is, for example, using the correct rules when making decisions. It is well known that humans are very poor at passive monitoring tasks where they are required to detect and respond to infrequent signals. These situations, called vigilance tasks, have been studied extensively by applied psychologists (see Warm, 1984). On the basis of this research, it is unlikely that people will be effective in the role of purely monitoring an automated system. 

Helium, the first member of the group, was detected in the spectrum of the Sun in 1868. Because of its low density (7 that of air), helium is used in all kinds of balloons and in synthetic atmospheres to make breathing easier for people suffering from emphysema. 

Successful theories typically both accommodate and predict. Most people, however, are more impressed by predictions than by accommodations. When Mendeleev produced a theory of the periodic table that accounted for all sixty [really sixty-two] known elements, the scientific community was only mildly impressed. When he went on to use his theory to predict the existence of two unknown elements that were then independently detected, the Royal Society awarded him its Davy Medal, . , Sixty accommodations paled next to two predictions, (Lipton, 1991, p, 134)... 

Educating the Patient and Family Nurses can do much to educate others on the importance of having their blood pressure checked at periodic intervals. This includes people of all ages because hypertension is not a disease seen only in older individuals. Once hypertension is detected, patient teaching becomes an important factor in successfully returning the blood pressure to normal or near normal levels. 

One study used quality-adjusted life years to capture the range of health-related dimensions that may affect the quality of life of patients. This measure also provides an estimate of the value or preferences for changes in health status (Neumann et al, 1999). The study used the Health Utility Index Mark II in a sample of patients and carers, which is a generic measure of the value of health-related quality of life. However, it is clear that further research is needed to explore (a) the key determinants or dimensions of quality of life that are important to people with dementia and their carers (b) whether existing instmments to measure and value health-related quality of life are able to detect differences in quality of life that are important to people with cognitive disability and their carers and (c) whether the assessment and... 

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