Causes of unintentional deaths from carbon monoxide poisonings in California.

The purpose of this study was to determine the annual number and incidence of unintentional deaths from carbon monoxide (CO) poisonings in California and to identify specific factors that caused or contributed to the deaths. Unintentional CO deaths in California over a ten-year period (1979 to 1988) were identified from the database of the California Master Mortality File and coroners' investigation reports. Factors associated with unintentional CO deaths were determined based on the information from the investigation reports. The annual number of unintentional CO deaths varied from 27 to 58 over the ten years examined, with an average annual death incidence of 1.7 x 10(-6). Death rates were high among males and African-Americans. Alcohol appeared to be a factor in 31% of the cases. The types of combustion sources associated with unintentional CO deaths were: heating or cooking appliances; motor vehicles; charcoal grills and hibachis; small engines; and camping equipment. Factors associated with unintentional CO deaths interact in a complex way. To reduce the rate of unintentional CO deaths effectively, joint efforts involving several prevention methods are suggested.

The distribution of lifetime cumulative exposures to radon for California residents.

The distribution of individual lifetime exposures to radon was estimated using data from studies on radon concentrations, mobility, and time-activity patterns in the state of California. The distributions of radon concentrations in various geographic regions were obtained from the results of year-long radon measurements of 310 residences. The mobility patterns were acquired through a survey of the moving histories of the members of 507 households. The indoor and outdoor time-activity data were collected for 1,780 individuals in 1,596 households. Based on these data, a computer simulation technique was used to estimate the distribution of radon exposures with a parametric (lognormal model) and a nonparametric approach (bootstrap method). The estimated average lifetime exposure for radon was 2,448 Bq.m-3.yr for the lognormal model and 2,487 Bq.m-3.yr for the bootstrap method. The standard deviation was 1,130 and 1,145 Bq.m-3.yr respectively. Assuming no move over the lifetime, the estimated average lifetime exposure to radon was 2,052 Bq.m-3.yr for the lognormal model and 2,078 Bq.m-3.yr for the bootstrap method, while the standard deviation increased to 1,378 Bq.m-3.yr for the lognormal model and 1,514 Bq.m-3.yr for the bootstrap method.

Unintentional carbon monoxide deaths in California from charcoal grills and hibachis.

This study was carried out to determine the annual incidence rate of and factors associated with unintentional deaths due to carbon monoxide (CO) poisoning from charcoal grills/hibachis in California during 1979-1988. A search through the California Master Mortality File was conducted to identify all cases with ICD-9 codes related to unintentional CO deaths. Individual coroners' investigation reports were obtained from 42 counties and evaluated by three evaluators. After excluding miscoded and misclassified cases, 444 deaths were judged to be authentic cases of unintentional CO poisoning. Among them, 59 deaths found to be due to the improper use of charcoal grills/hibachis. An increasing but not statistically significant trend was observed over the 10-year period. The highest rates occurred among males, asians, blacks, and middle-aged (20-39) people. Fifty-four percent of the deaths occurred in motor vehicles and 46% in residential structures.

Annual average radon concentrations in California residences.

A study was conducted to determine the annual average radon concentrations in California residences, to determine the approximate fraction of the California population regularly exposed to radon concentrations of 4 pCi/l or greater, and to the extent possible, to identify regions of differing risk for high radon concentrations within the state. Annual average indoor radon concentrations were measured with passive (alpha track) samplers sent by mail and deployed by home occupants, who also completed questionnaires on building and occupant characteristics. For the 310 residences surveyed, concentrations ranged from 0.10 to 16 pCi/l, with a geometric mean of whole-house (bedroom and living room) average concentrations of 0.85 pCi/l and a geometric standard deviation of 1.91. A total of 88,000 California residences (0.8 percent) were estimated to have radon concentrations exceeding 4 pCi/l. When the state was divided into six zones based on geology, significant differences in geometric mean radon concentrations were found between several of the zones. Zones with high geometric means were the Sierra Nevada mountains, the valleys east of the Sierra Nevada, the central valley (especially the southern portion), and Ventura and Santa Barbara Counties. Zones with low geometric means included most coastal counties and the portion of the state from Los Angeles and San Bernardino Counties south.

Irritant effects of formaldehyde exposure in mobile homes.

This paper reports the irritant effects associated with formaldehyde exposures in mobile homes. Week-long, integrated formaldehyde concentrations were measured using passive monitors in summer and winter while the mobile home residents continued their normal activities. Information on acute health problems, chronic respiratory/allergic illnesses, smoking behavior, demographic variables, and time spent at home was obtained on over 1000 individuals during the sampling period. Measured formaldehyde concentrations varied from under the limit of detection (0.01 ppm) to 0.46 ppm. Formaldehyde exposure was estimated for each individual by multiplying the concentration measured in his or her home by the time he or she spent at home. Irritant effects were found to be associated with formaldehyde exposure after controlling for age, sex, smoking status, and chronic illnesses using a logistic procedure. Some of the interaction terms found to be significant indicated that there were synergistic effects between formaldehyde exposure and chronic health problems.

Public inquiries about indoor air quality in California.

To identify the indoor air quality issues about which Californians most often sought advice from a health department or a public information agency and to evaluate how well these agencies met the public's needs, members of the California Interagency Working Group (IWG) on Indoor Air Quality kept records of inquiries they received over a 30-month period from mid-1985 through 1987. Members of the IWG answered calls from residents of a least 49 of California's 58 counties. IWG members received more public inquiries about residences than about offices, educational institutions, commercial buildings, or medical facilities. However, each call about a residence probably represented fewer people at risk of exposure to a real or a potential problem than did calls about other types of buildings. Homeowners themselves asked the majority of the questions about residences, whereas a large number of the inquiries about office buildings were made, not by affected office workers, but by building managers, contractors, consultants, or company health and safety officers. The leading topics of concern in the residences were asbestos, chemical and biological contamination, and radon. In offices, chemical contamination, the ventilation system, biological contamination, asbestos, and tobacco smoke were the most frequently mentioned sources of problems. Callers often reported experiencing headaches, allergy symptoms, nose or throat irritation, and respiratory tract problems in connection with their complaints. IWG members directed a third of the calls elsewhere, of which half were referred to consultants or testing laboratories. The IWG's experience in the State of California could help other health departments prepare to face the public's increasing concern about indoor air pollution.

Location of an extrinsic label in the primary and tertiary structure of bacteriorhodopsin.

We located a heavy metal label, mercurilated phenylglyoxal, in both the primary sequence and in the tertiary structure of bacteriorhodopsin. This label modified arginines 225 and 227, which are on the COOH-terminal helix (G). In the projected electron potential difference map, the major site is close to the central inner helix. From this result we conclude that helix 1 could not be the COOH-terminal helix G. We tested the multiple isomorphous replacement method for obtaining phases for purple membrane by electron diffraction.

Peptide-chain secondary structure of bacteriorhodopsin.

Ultraviolet circular dichroism spectroscopy in the interval from 190 to 240 nm and infrared spectroscopy in the region of the amide I band (1,600 cm-1 to 1,700 cm-1) has been used to estimate the alpha-helix content and the beta-sheet content of bacteriorhodopsin. Circular dichroism spectroscopy strongly suggests that the alpha-helix content is sufficient for only five helices, if each helix is composed of 20 or more residues. It also suggests that there is substantial beta-sheet conformation in bacteriorhodopsin. The presence of beta-sheet secondary structure is further suggested by the presence of a 1,639 cm-1 shoulder on the amide I band in the infrared spectrum. Although a structural model consisting of seven alpha-helical rods has been generally accepted up to this point, the spectroscopic data are more consistent with a model consisting of five alpha-helices and four strands of beta-sheet. We note that the primary amino acid sequence can be assigned to segments of alpha-helix and beta-sheet in a way that does not require burying more than two charged groups in the hydrophobic membrane interior, contrary to the situation for any seven-helix model.

Location of platinum binding sites on bacteriorhodopsin by electron diffraction.

A platinum-containing derivative of bacteriorhodopsin has been prepared by treating purple membranes with glycyl-L-methionatoplatinum. Low-dose electron diffraction was used to identify Pt binding sites in the 5.6 A resolution reconstruction of the bacteriorhodopsin unit cell in projection. This is a necessary first step in the use of the Pt derivative for identifying the parts of the amino acid sequence corresponding to the alpha helices in the bacteriorhodopsin structure and for obtaining phases for reflections out to 3.5 A resolution by the method of heavy-atom isomorphous replacement. The largest peak in a Fourier difference map between platinum-labeled and native purple membrane is larger than the spurious features expected to arise from errors in measurements of diffraction intensities.

High resolution cold stage for the JEOL 100B and 100C electron microscopes.

A high resolution, liquid nitrogen-cooled specimen stage has been designed and constructed for use on the JEOL 100B and 100C electron-microscopes. This stage will be useful for imaging biological macromolecular arrays in the frozen-hydrated or glucose-embedded states at low temperature. Images thus obtained should have an increased signal-to-noise ratio due to the radiation damage protection offered by low temperature.

Radiation damage of purple membrane at low temperature.

The intensities of diffracted electron beams for the purple membrane of Halobacterium halobium are found to decay exponentially as a function of the accumulated electron exposure, both at room temperature and at -120 degrees C. This permits us to define the "critical dose" Ne(h,k) for the (h,k) diffracted beam, as being the electron exposure (electrons/A2) at which the diffracteed intensity has fallen to e-1 of its initial value. The critical of purple membrane is found to increase from the room temperature value by at least a factor of four when the specimen is maintained at a temperature of -120 degrees C on a liquid-nitrogen-cooled stage. A relationship derived between the critical dose, Ne, and the dose for optimum imaging, Nopt. Both Ne and Nopt depend, of course, upon the spatial frequency, or resolution. The derivation is valid only for the case in which all sources of noise other than quantum fluctuations are neglected. In this case, Nopt approximately equal to 2.5Ne. Finally, Nuclear Track Emulsion plates have been shown to be advantageous for recording high resolution electron diffraction patterns of small (1 micrometer 2) patches of crystalline biological materials.

Molecular orientation of bacteriorhodopsin within the purple membrane of Halobacterium halobium.

The direction of orientation of the protein bacteriorhodopsin within the purple membrane of Halobacterium halobium has been determined by selected-area electron diffraction of membranes preferentially oriented by adsorption to polylysine. Purple membrane is known to adsorb preferentially to polylysine by its cytoplasmic surface at neutral pH and by its extracellular surface at low pH. To maintain the adsorbed membranes in a well-ordered state in the electron microscope, an improved technique of preparing frozen specimens was developed. Large areas of frozen-hydrated specimens, devoid of bulk water, were obtainable after the specimen was passed through a Ca stearate film at an air-water interface. High-resolution microscopy was used to relate the orientation observed in the electron diffraction patterns to the orientation of the projected structure that is obtained from images. We have found that the three-dimensional structure determined by Henderson and and Unwin [Henderson, R. & Unwin, P.N.T. (1975) Nature 257, 28--32] is oriented with the cytoplasmic side uppermost--i.e., the helices fan outward on the cytoplasmic side of the membrane.