We systematically reviewed the methods and correlation coefficients reported in studies with paired measurements of PM2.5 and CO personal exposures and/or cooking area concentrations in settings where biomass is the primary household fuel. We also obtained 2,048 paired PM2.5 and CO measurements from previously completed studies along with relevant information on season, level of urbanicity, fuel type, and other energy use behaviors to conduct pooled analyses of the PM2.5–CO relationship for personal exposures and cooking area concentrations. For the pooled analysis, our first objective was to evaluate the validity of exposure to CO as a surrogate of exposure to PM2.5 in epidemiologic and intervention studies of household air pollution. Because most health studies aim to evaluate daily or “usual” exposure, we limited our pooled analysis to studies of PM2.5 and CO concentration and/or exposure relationships for at least 24-hr in settings where biomass was the dominant household fuel. Our second objective was to evaluate whether the PM2.5–CO relationships estimated under one set of conditions are transportable to other conditions.
Methods: We assessed relationships between birth weight and pollutant concentrations during each infant’s first month of gestation and third trimester, as well as in each month of pregnancy using distributed lag models. We also conducted capture-area analyses limited to mothers residing within 4 miles (6.4 km) of each air quality monitoring station.
Rent ceiling laws are an example of how lack of motivation and incentives can discourage people from making sure their best work and resources go into their product or whatever they are doing.
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For example, if there is no incentive to motivate landlords to upkeep their property and make it the best it can be, they will left their properties at the lowest manageable state they can get away.
Using a surrogate mother, a women who bears a child for another women, makes it possible for couples to have a child with DNA from one or both of the intended parents.
Studies in Bolivia, Peru, Ghana, Kenya, Mexico, South Africa, the Philippines, and Burkina Faso (; ; ; ; ; ; ; ; ) measured CO exposure as a surrogate for PM2.5 without prior validation; one reason given was the strong PM2.5–CO exposure relationship observed in Guatemala (; ). Similarly, it is unknown whether the PM2.5–CO exposure relationship within a single study setting and population under one set of study conditions is transportable to other study conditions (e.g., pre- vs. postintervention; heating- vs. nonheating season) in the same setting and population, which is an approach taken in some studies (; ; ; ). Finally, it is unclear whether the PM2.5–CO correlation in cooking areas can be extrapolated to personal exposures in the same setting, which several studies have done (; ; ; ). Of these, only one () directly compared actual versus predicted PM2.5 exposure, finding no relationship (Pearson r=0.01).
Often couples turn to surrogacy if one or both are infertile (unable to reproduce), gay couples, or other medical conditions that cause the mother to be unable to conceive....
Validation study: a study in which data are simultaneously collected on the exposure surrogate (CO) and the gold standard method of exposure assessment (PM2.5). This study may be external to the main epidemiologic study, or be a subsample internal to the main study.
We provide a timely assessment of CO exposure as a surrogate of PM2.5 exposure, as a systematic review has been lacking but is critical to exposure measurement method selection for ongoing (; ; ; ; ) randomized controlled trials and other epidemiologic studies.
Accurate exposure assessment is the basis for evaluating exposure–response relationships (, ), and in the context of household air pollution, critical to interpreting the effectiveness of stove-fuel interventions (). Direct measurement of personal exposure to PM2.5 mass is considered the “gold standard” in epidemiologic studies (; ), but is challenging to measure in large populations () and in infants (; ). Questionnaires and cooking area PM2.5 have been used alone or in combination as surrogates but were poorly associated with personal PM2.5 exposure in validation studies (; ; ; ; ). As an alternative, many health and intervention studies have measured personal exposure to CO as a surrogate for PM2.5 given that it is also a major component of household air pollution but is easier and less costly to measure than PM2.5 (; ; ).
Recent research leads to the conclusion that aggressive promotion of safer sexual behavior and prevention and treatment of substance abuse could avert tens of thousands of new HIV infections and potentially save millions of dollars in health care costs.