Climate change threatens human health in many ways, through heat waves, extreme weather events, and shifts in disease vectors, as well as economic and social stresses on populations living in or trying to escape areas affected by seawater intrusion, drought, lower agricultural productivity, and floods.1 In the short term, most of these impacts could be substantially ameliorated by actions to reduce background disease risks and other known causes of vulnerability. The world beyond 2050 poses increasingly difficult challenges, not only because of the inherent uncertainties in long-term predictions, but because the extent and speed of change might exceed society's ability to adapt.
Child survival efforts can be effective only if they are based on accurate information about causes of deaths. Here, we report on a 4-year effort by WHO to improve the accuracy of this information.
WHO established the external Child Health Epidemiology Reference Group (CHERG) in 2001 to develop estimates of the proportion of deaths in children younger than age 5 years attributable to pneumonia, diarrhoea, malaria, measles, and the major causes of death in the first 28 days of life. Various methods, including single-cause and multi-cause proportionate mortality models, were used. The role of undernutrition as an underlying cause of death was estimated in collaboration with CHERG.
In 2000-03, six causes accounted for 73% of the 10.6 million yearly deaths in children younger than age 5 years: pneumonia (19%), diarrhoea (18%), malaria (8%), neonatal pneumonia or sepsis (10%), preterm delivery (10%), and asphyxia at birth (8%). The four communicable disease categories account for more than half (54%) of all child deaths. The greatest communicable disease killers are similar in all WHO regions with the exception of malaria; 94% of global deaths attributable to this disease occur in the Africa region. Undernutrition is an underlying cause of 53% of all deaths in children younger than age 5 years.
Achievement of the millennium development goal of reducing child mortality by two-thirds from the 1990 rate will depend on renewed efforts to prevent and control pneumonia, diarrhoea, and undernutrition in all WHO regions, and malaria in the Africa region. In all regions, deaths in the neonatal period, primarily due to preterm delivery, sepsis or pneumonia, and birth asphyxia should also be addressed. These estimates of the causes of child deaths should be used to guide public-health policies and programmes.
Rationale: In late October 2003, Southern California wildfires burned more than 3,000 km2. The wildfires produced heavy smoke that affected several communities participating in the University of Southern California Children's Health Study (CHS). Objectives: To study the acute effects of fire smoke on the health of CHS participants. Methods: A questionnaire was used to assess smoke exposure and occurrence of symptoms among CHS high-school students (n = 873; age, 17-18 yr) and elementary-school children (n = 5,551; age, 6-7 yr), in a total of 16 communities. Estimates of particulate matter (PM10) concentrations during the 5 d with the highest fire activity were used to characterize community smoke level. Main Results: All symptoms (nose, eyes, and throat irritations; cough; bronchitis; cold; wheezing; asthma attacks), medication usage, and physician visits were associated with individually reported exposure differences within communities. Risks increased monotonically with the number of reported smoky days. For most outcomes, reporting rates between communities were also associated with the fire-related PM10 levels. Associations tended to be strongest among those without asthma. Individuals with asthma were more likely to take preventive action, such as wearing masks or staying indoors during the fire. Conclusions: Exposure to wildfire smoke was associated with increased eye and respiratory symptoms, medication use, and physician visits.
BACKGROUND/OBJECTIVES: Zinc is an essential micronutrient and deficiency can lead to an increased risk for infectious diseases and growth retardation among children under 5 years of age. We aimed to estimate disease-specific and all-cause mortality attributable to zinc deficiency. SUBJECT/METHODS: We estimated the prevalence of zinc deficiency in Latin America, Africa and Asia, where based on zinc availability in the diet and childhood stunting rates, zinc deficiency is widespread. The relative risks of death among zinc-deficient children for diarrhea, malaria and pneumonia were estimated from randomized controlled trials. We used the comparative risk assessment methods to calculate deaths and burden of disease (measured in disability-adjusted life years, DALYs) from each of these three diseases attributable to zinc deficiency in these regions. RESULTS: Zinc deficiency was responsible for 453,207 deaths (4.4% of childhood deaths), and 1.2% of the burden of disease (3.8% among children between 6 months and 5 years) in these three regions in 2004. Of these deaths, 260,502 were in Africa, 182,546 in Asia and 10,159 in Latin America. Zinc deficiency accounted for 14.4% of diarrhea deaths, 10.4% of malaria deaths and 6.7% of pneumonia deaths among children between 6 months and 5 years of age. CONCLUSIONS: Zinc deficiency contributes to substantial morbidity and mortality, especially from diarrhea. Zinc supplementation provided as an adjunct treatment for diarrhea may be the best way to target children most at risk of deficiency.
The greater the potential for disastrous, large-scale, or catastrophic impacts on health, the greater the case for precaution. The imperative for precautionary action, critical also for downstream determinants of health, is at least as compelling where macro-level concerns about the sustainability of life on Earth are at issue. In this context, I propose that a higher threshold of uncertainty is needed where large-scale harms to health and well-being are possible. Initial efforts must focus on the training of researchers and risk managers for competencies in complexity, and in systems approaches to transdisciplinary enquiry. Revisiting the intent behind Bradford Hill on causation is an essential first step. Focus on the more proximate causes of diseases, such as those related either to occupational exposures or to more downstream environmental exposures, is left to others in this collection.