Key issues in public health surveillance for the 1990s.

In this paper, we have proposed a wider scope for public health surveillance in order to incorporate demographic and health-system monitoring, along with activities conventionally associated with epidemiologic surveillance. This new conception stems, in turn, from a revised definition of public health, which describes, not a sector of activity or a type of health service, but a level of aggregation based on the population at large. In our review of the ideas that lead to the institutionalization of health surveillance, we have stressed the broad concepts developed by such pioneers as Graunt and Petty. Their original concepts emerged from their active concerns for the public's health at a time when no scientific theory of contagion was available, let alone any knowledge about how to treat persons for the major diseases. Later on, largely as the result of impressive advances in biomedical knowledge, public health surveillance tended to specialize and to concentrate predominantly on disease outbreaks and on salient adverse health conditions. Health surveillance became closely associated with epidemiologic surveillance, which in turn became associated with the ability to respond promptly to adverse health outcomes. Recently, we have witnessed a gradual broadening of both the concepts and the practice of health surveillance. Paradoxically, the new currents tend to recapture some of the spirit and scope of the early definitions, prompted perhaps by grave historical parallels--we face newly emerging health problems for which we have no clear-cut solutions. If one element needs to be stressed to promote the objectives of health surveillance today, it is that we need the ability to anticipate health outcomes and not just respond to them. This, in turn, requires that we give more weight to the surveillance of risk factors and that we increase our understanding of the complex causal interrelationships that link exposure to risk factors--including behavioral, life-style, and environmental ones--with adverse health conditions and disability. Needless to say, the first and foremost aim of health care--and modern surveillance is one of the tools needed to achieve this aim--is to promote the well-being of individuals while improving their health.

Mortality of a cohort of workers in the styrene-butadiene polymer manufacturing industry (1943-1982).

A cohort of 12,110 male workers employed 1 or more years in eight styrene-butadiene polymer (SBR) manufacturing plants in the United States and Canada has been followed for mortality over a 40-year period, 1943 to 1982. The all-cause mortality of these workers was low [standardized mortality ratio (SMR) = 0.81] compared to that of the general population. However, some specific sites of cancers had SMRs that exceeded 1.00. These sites were then examined by major work divisions. The sites of interest included leukemia and non-Hodgkin's lymphoma in whites. The SMRs for cancers of the digestive tract were higher than expected, especially esophageal cancer in whites and stomach cancer in blacks. The SMR for arteriosclerotic heart disease in black workers was significantly higher than would be expected based on general population rates. Employees were assigned to a work area based on job longest held. The SMRs for specific diseases differed by work area. Production workers showed increased SMRs for hematologic neoplasms and maintenance workers, for digestive cancers. A significant excess SMR for arteriosclerotic heart disease occurred only in black maintenance workers, although excess mortality from this disease occurred in blacks regardless of where they worked the longest. A significant excess SMR for rheumatic heart disease was associated with work in the combined, all-other work areas. For many causes of death, there were significant deficits in the SMRs.

Exposure assessment for workers applying DDT to control malaria in Veracruz, Mexico.

DDT has systematically been used in sanitation campaigns against malaria in Mexico. To assess chronic occupational exposure, we studied a group of workers dedicated to spraying houses to control malaria vectors in the state of Veracruz. Exposure was directly estimated for a subgroup of 40 workers by measuring DDT metabolites in adipose tissue samples and indirectly estimated for 331 workers by using a questionnaire to determine their occupational history. Participants ranged in age from 20 to 70 years, and 80% of the workers had been employed in the sanitation campaign for at least 20 years. The mean concentrations of extractable lipids found in adipose tissue samples were as follows: total DDT, 104.48 micrograms/g; p,p'-DDE, 60.98 micrograms/g; p,p'-DDT, 31.0 micrograms/g; o,p'-DDT, 2.10 micrograms/g; and p,p'-DDD, 0.95 microgram/g. The DDT metabolite p,p'-DDE was selected as the indicator of chronic exposure. An index of chronic occupational exposure was constructed according to worker position and based on the historical duration and intensity of DDT application. A linear model including this index, the use of protective gear, and recent weight loss explained 55% of the variation of p,p'-DDE concentrations in adipose tissue. By this model, the predicted values of p,p'-DDE concentration in adipose tissue for the 331 workers are between 9.56 micrograms/g and 298.4 micrograms/g of fat, with a geometric mean of 67.41 micrograms/g. These high levels of DDT in adipose tissue call for exposure prevention programs and the promotion of more secure application measures and hygiene. We also discuss the use of indirect measures of DDT exposure in epidemiological studies of health effects.

Lymphohematopoietic cancers and butadiene and styrene exposure in synthetic rubber manufacture.

The described nested case-control study of lymphohematopoietic cancers occurring in a cohort of synthetic rubber production workers was conducted to determine the associations of these cancers with exposure to butadiene and styrene. Cases have been confirmed through hospital record review of 95 percent of the cancers. Exposures are based on measured values of the two chemicals from personal monitoring data in seven of the eight plants under study. The results indicate that the risk of leukemia increases with exposure to a time-weighted average butadiene measure. The odds ratio at only 1 ppm average butadiene exposure is 1.50 (95% CI 1.07, 2.10). Work in specific areas also contributes to the risk, possibly because these areas have not been completely characterized for differences in butadiene exposure. Hodgkins disease is also associated with butadiene exposure. Multiple myeloma, lymphosarcoma, and all lymphomas are associated with exposure to styrene. Since workers in this industry are apparently exposed to two carcinogenic agents, further effort must be made to distinguish the exposures to each chemical over time and to characterize their interrelationship with the risk of cancers of the lymphohematopoietic system.

Potential force of infection of human rabies transmitted by vampire bats in the Amazonian region of Brazil.

Human rabies transmitted by bats has acquired greater epidemiologic relevance in various Latin American countries, just when cases transmitted by dogs have decreased. Concern has been heightened by reports of increased rates of bats biting humans in villages in the Amazonian region of Brazil. The aim of the present work was to estimate the potential force of infection (per capita rate at which susceptible individuals acquire infection) of human rabies transmitted by the common vampire bat if the rabies virus were to be introduced to a colony of bats close to a village with a high rate of human bites. The potential force of infection could be then used to anticipate the size of a rabies outbreak in control programs. We present an estimator of potential incidence, adapted from models for malaria. To obtain some of the parameters for the equation, a cross-sectional survey was conducted in Mina Nova, a village of gold prospectors in the Amazonian region of Brazil with high rates of bates biting humans. Bats were captured near dwellings and sent to The Rabies Diagnostic Laboratory at the Center for Control of Zoonoses (Sao Paulo, Brazil) to be examined. To estimate the force of infection, a hypothetical rabies outbreak among bats was simulated using the actual data obtained in the study area. Of 129 people interviewed, 23.33% had been attacked by a vampire bat during the year prior to the study, with an average of 2.8 bites per attacked person. Males (29.41%) were attacked more often than females (11.36%); also, adults (29.35%) were attacked more often than children (8.33%). None of the 12 bats captured in Mina Nova tested positive for rabies, but the force of infection for a hypothetical outbreak was estimated to be 0.0096 per person per year. This risk represents 0.96 cases per 100 area residents, giving an incidence of 1.54 cases of bat-transmitted human rabies per year in the village of Mina Nova (160 inhabitants). The estimated risk is comparable with what has been observed in similar Brazilian villages.

Developing consensus: mercury science and policy in the NAFTA countries (Canada, the United States and Mexico).

The international science community has recognized methylmercury in the aquatic food chain, as a potential environmental and human health risk. As a result, countries around the world have implemented a number of mercury management initiatives. The United States, Mexico and Canada in consultation with stakeholders are developing a trilateral North American Regional Action Plan (NARAP) on mercury. Through public involvement in the decision making process, the NARAP has offered opportunities for more transparency in transactions between governments, industry and stakeholders. In spite of the available scientific information, there are still important uncertainties associated with the mercury issue. These knowledge gaps include: the most appropriate methylmercury reference dose for sensitive groups; the percentage of the North American population that is at risk from methylmercury exposure; spatial and temporal mercury deposition patterns in each country; the link between mercury emissions, atmospheric deposition and methylmercury concentrations in fish; and the relative magnitude of contributions from natural and anthropogenic sources.

Selecting high-priority hazardous chemicals for tri-national control: a maximum-utility method applied to Mexico.

The dispersion of persistent, bioaccumulative toxic chemicals poses risks to human health and the integrity of the ecosystem on a continental scale. Mexico, the United States, and Canada sought to add two pollutants to an existing list of four subject to North American Regional Action Plans (chlordane, DDT, mercury, PCBs). Mexican negotiators used results from an internal selection process, applying 14 criteria in five categories-physicochemical, health-endpoint, data quality/quantity, exposure potential, and control feasibility-to a baseline group of over 4,700 substances. Using policy analysis by the multiattribute maximum-utility method, progressive application of criteria and weighting algorithms acted like successive filters to identify priority lists of 15 and 7 substances/substance groups for Mexico. The 15 are: 1) benzo-a-pyrene (1 other PAHs); 2) cadmium; 3) heptachlor; 4) hexachlorobenzene; 5) lead; 6) lindane (+ other HCH isomers); 7) 2,3, 7,8-tetrachlorodibenzo-p-dioxin (&plus other PCDDs); 8) aldrin; 9) arsenic; 10) chromium; 11) carbon tetrachloride; 12) 3-3'-dichlorobenzidine; 13) dieldrin; 14) nickel; and 15) toxaphene. The first seven are the priority list of seven.

Household firewood use and the health of children and women of Indian communities in Chiapas, Mexico.

A follow-up study in two rural communities in the state of Chiapas, Mexico, compared families that used an improved stove for cooking with those that used traditional open-fire stoves, to assess the risks of respiratory symptoms in children and women exposed to wood smoke. 16-hour measurements showed that the concentration of particles less than 10 microm in diameter was significantly lower in households with the better stoves in the kitchen area, where children usually play, i.e., 158 microg/m3 vs 305 microg/m3 (p = 0.03). Multivariate models showed that using the better stove tended to protect against symptoms such as the common cold in children (RR 0.24; 9.5% CI 0.05, 1.02). Use of more firewood was linked to greater risks of experiencing difficulty breathing (RR 1.15; 95% CI 1.04, 1.27) and the common cold (RR 1.09; 95% CI 1.01, 1.18) in women. The use of stoves that require less wood for cooking reduces the risks of respiratory symptoms that may contribute to complicated respiratory diseases and mortality.

Common vampire bat attacks on humans in a village of the Amazon region of Brazil.

Many people in Amazonian communities have reported bat bites in the last decade. Bites by vampire bats can potentially transmit rabies to humans. The objective of this study was to analyze factors associated with bat biting in one of these communities. A cross-sectional survey was conducted in a village of gold miners in the Amazonian region of Brazil (160 inhabitants). Bats were captured near people's houses and sent to a lab. Of 129 people interviewed, 41% had been attacked by a bat at least once, with 92% of the bites located on the lower limbs. A logistic regression found that adults were bitten around four times more often than children (OR = 3.75, CI 95%: 1.46-9.62, p = 0.036). Males were bitten more frequently than females (OR = 2.08, CI 95%: 0.90-4.76, p = 0.067). Nine Desmodus rotundus and three frugivorous bats were captured and tested negative for rabies. The study suggests that, in an area of gold miners, common vampire bats are more likely to attack adults and males. The control strategy for human rabies developed in this region should therefore place special emphasis on adult males. There should also be more research on how the search for gold in the Amazonian region places people and the environment at risk.

[Treatment of human rabies: a summary of its history]. / Tratamiento contra la rabia humana: un poco de su historia.

A historical review of the treatment of human rabies from ancient times up to the present is undertaken. An attempt is made to trace parallel between the concept of the main cause of rabies in a certain period and the kind of treatment utilized. The ancient Greek goddess Artemis was considered to be a healer of rabies; they already identified wound cauterization. People of the first century A.D. knew of the infection deriving from the saliva of a rabid dog and called it virus (in Latin). During medieval times when a magical and religious concept regarding health was prevalent, the principal protector was called St. Humbert. During the Renaissance many experiments were carried out and new information on the disease was obtained, both were basic in opening the way for new findings in the future. At that time the miasmatic and contagious theories were predominant. Pasteur strongly objected to the idea of the spontaneity of rabies. At the end of the XIXth. century and based on microbial discoveries, Pasteur brought about a great scientific revolution as regards the possibility of treating rabies by using a vaccine. At the present time, vaccines are of the nervous type or not, and the recommended dose varies. A large-number of studies on vaccination have been undertaken. In Latin America the most used are those by Fuenzalida and Palacios. At present, WHO recommends the vaccine made by cell culture.

[Economic evaluation and decision making in environmental health]. / Evaluación económica y toma de decisiones en salud ambiental.

Due to the increasing deterioration of the environment and its possible consequences for the health of the population the design and implementation of policies for the control of economic activities according to criteria for the protection of human health and the environment itself have become an unquestionable need. Such policies would include the economic feasibility of existing alternatives for protection. Due to the huge interests involved, however, other factors, both social and political should also be taken into consideration. Economic evaluation has been seen as a promising foundation for the decision making process in this subject. This tool's capacity systematically to organize and compare the costs and the benefits of the alternatives for the solution of environmental problems is analysed. The main characteristics of cost-benefit and cost-effectiveness studies are summarized, as well as the possible forms of economic evaluation, of the environment and the details of this field for the application of such techniques of analysis. The limits of these tools for the quantification of the non-monetary costs of environmental risks and the consequent damage to health, whether as pain, suffering or the disability of non-economic ally active persons are set out as these constitute the methodological challenge of the economic evaluation in the area. The importance of the enhancement of information input for the decision-making process relating to environmental health issues such as the distributions of costs and benefits among the different social groups is scrutinized. Lastly, the growing political concern with environment issues is stated, as well as the technical possibility of the manipulation of these analytical tools. On the basis of these elements, the need for evaluators to be conscious on the political implications of their studies, as well as the importance of their relationship with the decision-makers in view of the need for effective relevance to current environmental issues.

[Particle exposure modeling in the general population and risk of respiratory disease]. / Modelaje de exposición a partículas en población general y riesgo de enfermedad respiratoria.

Total exposure assessment identifies the various sources of exposure to air pollution which affect each individual, thus functioning as a useful tool in clinical and environmental exposure management. A cross sectional survey was performed in order to create a total exposure model of inhaled particulates. This survey involved 544 subjects located within the Mexico City Merced monitoring station, an area covering three kilometers in diameter. Two questionnaires were developed one on housing and the other on respiratory symptoms. A diary on daily activity was kept, and an outdoor monitoring station was also installed. A new technology was adapted and incorporated for personal and indoor monitoring. A correlation of up to 0.38 was identified between the environmental concentrations. Exposures at home and at other extramural activities are most predictive of personal exposure. It was determined that 8.8% of the subjects studied had chronic bronchitis, and that this percentage increases with greater levels of exposure and outdoor sports. These findings conclude that the models are useful for risk assessment and management in Mexico.

[Considerations on human rabies transmitted by bats]. / Algunas consideraciones sobre la rabia humana transmitida por murciélago.

The purpose of this study is to present a combined analysis of eight outbreaks of human rabies transmitted by bats in Brazil and Peru. Some factors present in many outbreaks were identified, as follows: most of the outbreaks occurred in small villages in the rural Amazonian region; there was a change of local production processes; little or no cattle was present; the houses were vulnerable; access to health services was difficult. Other information was also analyzed, for instance: attack rate; incubation period; site of the attack; occupation, sex and age of the victim. As part of the study of these recent outbreaks, a review of the bibliography on human rabies transmitted by bats was also carried out.

[Diabetes mellitus and the health care transition]. / La diabetes mellitus y la transición de la atención a la salud.

To document the existence of an epidemiologic and a health care transition in Mexico, diabetes mellitus (DM) mortality was analyzed. Age and sex adjusted mortality rates were estimated for each one of the states of Mexico, as well as the mean age at death, the number of years of potential life lost, and their percent distribution. The geographic distribution of these variables was plotted in maps according to tertiles or quartiles. The proportion of deaths due to acute and chronic complications of DM was classified according to community size. Polarized patterns of DM mortality as well as in the percentage contribution of deaths due to its acute and chronic complications were observed, in agreement with the postulated transitional process.

Lymphohematopoietic cancer in styrene-butadiene polymerization workers.

1,3-Butadiene and styrene are suspected carcinogens and common chemicals used in the synthesis of rubber. To investigate any potential human hazards from exposure to these chemicals, a case-control study of 59 lymphohematopoietic cancers was conducted within a cohort of male workers employed between 1943 and 1982 in eight North American styrene-butadiene rubber polymer-producing plants. A total of 193 controls were matched to the cases by plant, age, year of hire, duration worked, and survival to time of death of the case. Each job was assigned an estimated exposure rank, and each worker's cumulated rank score was calculated on the basis of the time spent in each job throughout his employment. "Exposure" as a dichotomous variable was defined as a log rank score above the mean of the log scores for the total population of cases and controls within a subtype of cancer. Matched-pair analysis identified a strong association between leukemia and butadiene, with an odds ratio of 9.36 (95% confidence interval 2.05-22.9) and an association between styrene and leukemia (odds ratio = 3.13, 95% confidence interval 0.84-11.2) that did not achieve statistical significance. When exposure to both styrene and butadiene was included in a conditional logistic regression model, the odds ratio for butadiene remained high (odds ratio = 7.39), but the estimated association of leukemia with styrene was small. The results of this study support the hypothesis that exposure to butadiene is associated with the risk of leukemia. There also appears to be an additional risk from work in specific subdivisions of the industry.

Use of lead-glazed ceramics is the main factor associated to high lead in blood levels in two Mexican rural communities.

Two isolated rural communities of Mexico were studied to assess the possible relationship between lead-glazed ceramics use and lead exposure. Women from these communities (n = 98) were asked to participate by filling out a general-purpose and exposure questionnaire in order to assess the individual contribution of ceramics to lead exposure. Blood samples were withdrawn to measure lead in blood and erythrocytic zinc protoporphyrin levels. Results were analyzed by multiple regression in order to find predictors of the dependent variables. Significant association between lead in blood and erythrocytic zinc protoporphyrin levels was identified with the following variables: storage in lead-glazed ceramics, cooking in lead-glazed ceramics, and meat and cheese consumption. The adjusted regression models explained 20-23% of the variance of the dependent variables (lead in blood and erythrocytic zinc protoporphyrin). A significant association (r2 = .38) was observed between lead in blood and lead in food prepared in lead-glazed ceramics in a subsample of 28 women. Results indicate that lead-glazed ceramics use may be the main predictor of lead in blood and erythrocytic zinc protoporphyrin levels in the rural communities studied.

[Serum cholesterol and diabetes mellitus: main independent risk factors of ischemic heart disease mortality in Mexico]. / Colesterol sérico y diabetes mellitus: principales factores de riesgo independientes en la mortalidad por cardiopatía isquémica en México.

In order to evaluate the contribution of hypertension, diabetes, smoking and serum cholesterol on coronary heart disease mortality in Mexico, an ecologic study was developed. Mortality rates of coronary heart disease (CHD), diabetes and hypertension; the proportion of people smoking six or more cigarettes daily; and the mean serum cholesterol levels, were recorded for each of the states of Mexico. All variables were included in a multiple linear regression model, taking CHD mortality as the dependent variable. All variables explained more than two thirds of the occurrence of CHD mortality. However either using a backward or a forward method, only serum cholesterol and diabetes mortality had a significative contribution on CHD mortality (re = 0.65; F = 27; p < 0.0001). Coronary heart disease mortality in Mexico has shown an increasing trend in the last 50 years. Mexican-americans in the United States have a high prevalence of major risk factors, but few studies have done to assess its contribution in Mexicans living in Mexico. This increase may be explained by an increase in the occurrence of diabetes and the still denied importance of high serum cholesterol.

Cancer epidemiology among styrene-butadiene rubber workers.

The standardized mortality ratios for some cancers of the lymphohaematopoietic system were high in an early cohort analysis. Since the presence of large numbers of unexposed workers could conceal risks within a cohort, a case-control study was designed to examine the relationship between estimated exposures and the occurrence of these cancers. The results suggested that the risk for leukaemia was associated with exposure to butadiene and with work in specific areas. Modelling, using rank scores, indicated an increase in the risk for leukaemia with increasing exposure score. Use of cases validated by review of hospital records and selection of a new set of controls did not change the findings. The data indicated that comparison of scores within the same time frame improved the model and increased the estimated odds ratio, suggesting that exposure time or dose rate may prove to be the important variable for risk. Exact measurements from the companies involved showed significant correlations between assigned ranks and level of exposure derived from personal monitoring for butadiene but not for styrene. Thus, use of the measured values might be expected to show an association between leukaemia and exposure to butadiene. The standardized mortality ratio for leukaemia among long-term workers hired before 1960 who had worked in the three plants where the geometric mean butadiene level was three to five times higher than those in the other plants is 1.8 times higher than that of the US population. An appropriate algorithm for comparing cases and controls on the bases of the measured samples is being developed.