Inhalable desert dust, urban emissions, and potentially biotoxic metals in urban Saharan-Sahelian air.

Saharan dust incursions and particulates emitted from human activities degrade air quality throughout West Africa, especially in the rapidly expanding urban centers in the region. Particulate matter (PM) that can be inhaled is strongly associated with increased incidence of and mortality from cardiovascular and respiratory diseases and cancer. Air samples collected in the capital of a Saharan-Sahelian country (Bamako, Mali) between September 2012 and July 2013 were found to contain inhalable PM concentrations that exceeded World Health Organization (WHO) and US Environmental Protection Agency (USEPA) PM2.5 and PM10 24-h limits 58 - 98% of days and European Union (EU) PM10 24-h limit 98% of days. Mean concentrations were 1.2-to-4.5 fold greater than existing limits. Inhalable PM was enriched in transition metals, known to produce reactive oxygen species and initiate the inflammatory response, and other potentially bioactive and biotoxic metals/metalloids. Eroded mineral dust composed the bulk of inhalable PM, whereas most enriched metals/metalloids were likely emitted from oil combustion, biomass burning, refuse incineration, vehicle traffic, and mining activities. Human exposure to inhalable PM and associated metals/metalloids over 24-h was estimated. The findings indicate that inhalable PM in the Sahara-Sahel region may present a threat to human health, especially in urban areas with greater inhalable PM and transition metal exposure.

Persistent organic contaminants in Saharan dust air masses in West Africa, Cape Verde and the eastern Caribbean.

Anthropogenic semivolatile organic compounds (SOCs) that persist in the environment, bioaccumulate, are toxic at low concentrations, and undergo long-range atmospheric transport (LRT) were identified and quantified in the atmosphere of a Saharan dust source region (Mali) and during Saharan dust incursions at downwind sites in the eastern Caribbean (U.S. Virgin Islands, Trinidad and Tobago) and Cape Verde. More organochlorine and organophosphate pesticides (OCPPs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyl (PCB) congeners were detected in the Saharan dust region than at downwind sites. Seven of the 13 OCPPs detected occurred at all sites: chlordanes, chlorpyrifos, dacthal, dieldrin, endosulfans, hexachlorobenzene (HCB), and trifluralin. Total SOCs ranged from 1.9-126 ng/m(3) (mean = 25 ± 34) at source and 0.05-0.71 ng/m(3) (mean = 0.24 ± 0.18) at downwind sites during dust conditions. Most SOC concentrations were 1-3 orders of magnitude higher in source than downwind sites. A Saharan source was confirmed for sampled air masses at downwind sites based on dust particle elemental composition and rare earth ratios, atmospheric back trajectory models, and field observations. SOC concentrations were considerably below existing occupational and/or regulatory limits; however, few regulatory limits exist for these persistent organic compounds. Long-term effects of chronic exposure to low concentrations of SOCs are unknown, as are possible additive or synergistic effects of mixtures of SOCs, biologically active trace metals, and mineral dust particles transported together in Saharan dust air masses.

Saharan dust - a carrier of persistent organic pollutants, metals and microbes to the Caribbean? / Polvo sahariano: ¿portador de contaminantes orgánicos persistentes, metales y microbios al Caribe?

An international team of scientists from government agencies and universities in the United States, U.S. Virgin Islands (USVI), Trinidad & Tobago, the Republic of Cape Verde, and the Republic of Mali (West Africa) is working together to elucidate the role Saharan dust may play in the degradation of Caribbean ecosystems. The first step has been to identify and quantify the persistent organic pollutants (POPs), trace metals, and viable microorganisms in the atmosphere in dust source areas of West Africa, and in dust episodes at downwind sites in the eastern Atlantic (Cape Verde) and the Caribbean (USVI and Trinidad & Tobago). Preliminary findings show that air samples from Mali contain a greater number of pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) and in higher concentrations than the Caribbean sites. Overall, POP concentrations were similar in USVI and Trinidad samples. Trace metal concentrations were found to be similar to crustal composition with slight enrichment of lead in Mali. To date, hundreds of cultureable micro-organisms have been identified from Mali, Cape Verde, USVI, and Trinidad air samples. The sea fan pathogen, Aspergillus sydowii, has been identified in soil from Mali and in air samples from dust events in the Caribbean. We have shown that air samples from a dust-source region contain orders of magnitude more cultureable micro-organisms per volume than air samples from dust events in the Caribbean, which in turn contain 3-to 4-fold more cultureable microbes than during non-dust conditions. Rev. Biol. Trop. 54 (Suppl. 3): 9-21. Epub 2007 Jan. 15.

Un grupo internacional de agencias gubernamentales y universidades de los Estados Unidos, las Islas Vírgenes (EUA), Trinidad y Tobago, la República de Cabo Verde y la República de Mali (África Oeste), está trabajando en conjunto para elucidar el papel que el polvo del Sahara puede estar jugando en el deterioro de los ecosistemas caribeños. El primer paso ha sido identificar y cuantificar los Contaminantes Orgánicos Persistentes (POPs, por sus siglas en inglés), los metales traza y los microorganismos viables presentes en la atmósfera de las áreas fuente de polvo de África occidental y en áreas ubicadas en la dirección del viento, como el Atlántico este (Cabo Verde) y el Caribe (IVEUA y Trinidad y Tobago), durante los episodios de transporte de polvo. Resultados preliminares indican que las muestras de aire de Mali contienen mayor número y mayores concentraciones de pesticidas, bifenilos policlorinados (PCBs) e hidrocarburos policíclicos aromáticos (PAHs) que las de los sitios del Caribe. Las concentraciones de POPs fueron similares en las muestras de USVI y de Trinidad. Se encontró que las concentraciones de metales traza fueron similares a las de la composición de la corteza, con un ligero enriquecimiento de plomo en Mali. Hasta la fecha, cientos de microorganismos cultivables han sido identificados en las muestras de Mali, Cabo Verde, IVEUA y Trinidad. Hallamos el patógeno de los abanicos de mar, Aspergillus sydowi, en las muestras de aire de Mali y en las muestras del Caribe durante polvaredas. Hemos demostrado que las muestras de aire provenientes de una región fuente de polvo, contienen más microorganismos cultivables por volumen -en órdenes de magnitud- que las muestras de aire tomadas en polvaredas en el Caribe, las cuales a su vez contienen tres a cuatro veces más microorganismos cultivables que aquellas tomadas cuando no hay polvaredas.

Pesticides in the atmosphere of the Mississippi River Valley, part I--rain.

Weekly composite rainfall samples were collected in three paired urban and agricultural regions of the Midwestern United States and along the Mississippi River during April-September 1995. The paired sampling sites were located in Mississippi, Iowa, and Minnesota. A background site, removed from dense urban and agriculture areas, was located near Lake Superior in Michigan. Herbicides were the predominant type of pesticide detected at every site. Each sample was analyzed for 47 compounds and 23 of 26 herbicides, 13 of 18 insecticides, and three of three related transformation products were detected in one or more sample from each paired site. The detection frequency of herbicides and insecticides were nearly equivalent at the paired Iowa and Minnesota sites. In Mississippi, herbicides were detected more frequently at the agricultural site and insecticides were detected more frequently at the urban site. The highest total wet depositional amounts (microg pesticide/m2 per season) occurred at the agricultural sites in Mississippi (1980 microg/m2) and Iowa (490 microg/m2) and at the urban site in Iowa (696 microg/m2). Herbicides accounted for the majority of the wet depositional loading at the Iowa and Minnesota sites, but methyl parathion (1740 microg/m2) was the dominant compound contributing to the total loading at the agricultural site in Mississippi. Atrazine, CIAT (a transformation product of atrazine and propazine) and dacthal were detected most frequently (76, 53, and 53%, respectively) at the background site indicating their propensity for long-range atmospheric transport.

Pesticides in the atmosphere of the Mississippi River Valley, part II--air.

Weekly composite air samples were collected from early April through to mid-September 1995 at three paired urban and agricultural sites along the Mississippi River region of the Midwestern United States. The paired sampling sites were located in Mississippi, Iowa, and Minnesota. A background site, removed from dense urban and agricultural areas, was located on the shore of Lake Superior in Michigan. Each sample was analyzed for 49 compounds; of these, 21 of 26 herbicides, 13 of 19 insecticides, and 4 of 4 related transformation products were detected during the study, with most pesticides detected in more than one sample. The maximum number of pesticides detected in an air sample was 18. Herbicides were the predominant type of pesticide detected at every site. Detection frequencies of most herbicides were similar at the urban and agricultural sites in Iowa and Minnesota. In Mississippi, herbicides generally were detected more frequently at the agricultural site. The insecticides chlorpyrifos, diazinon, and carbaryl, which are used in agricultural and non-agricultural settings, were detected more frequently in urban sites than agricultural sites in Mississippi and Iowa. Methyl parathion was detected in 70% of the samples from the Mississippi agricultural site and at the highest concentration (62 ng/m3 air) of any insecticide measured in the study. At the background site, dacthal (100%), atrazine (35%), cyanazine (22%), and the (primarily atrazine) triazine transformation products CIAT (35%) and CEAT (17%) were detected most frequently, suggesting their potential for long-range atmospheric transport.

Occurrence of pesticides in rain and air in urban and agricultural areas of Mississippi, April-September 1995.

In April 1995, the US Geological Survey began a study to determine the occurrence and temporal distribution of 49 pesticides and pesticide metabolites in air and rain samples from an urban and an agricultural sampling site in Mississippi. The study was a joint effort between the National Water-Quality Assessment and the Toxic Substances Programs and was part of a larger study examining the occurrence and temporal distribution of pesticides in air and rain in the Mississippi River basin. Concurrent high-volume air and wet-only deposition samples were collected weekly. The air samplers consisted of a glass-fiber filter to collect particles and tandem polyurethane foam plugs to collect gas-phase pesticides. Every rain and air sample collected from the urban and agricultural sites had detectable levels of multiple pesticides. The magnitude of the total concentration was 5-10 times higher at the agricultural site as compared to the urban site. The pesticide with the highest concentration in rain at both sites was methyl parathion. The pesticide with the highest concentration in the air samples from the agricultural site was also methyl parathion, but from the urban site the highest concentration was diazinon followed closely by chlorpyrifos. More than two decades since p,p'-DDT was banned from use in the United States, p,p'-DDE, a metabolite of p,p'-DDT, was detected in every air sample collected from the agricultural site and in more than half of the air samples from the urban site.