| Summary: | Air pollution has many adverse effects on health and is associated with an increased risk of mortality. Desert dust outbreaks contribute directly to air pollution by increasing particulate matter concentrations. We investigated the influence of desert dust outbreaks on air quality in Santa Cruz de Tenerife, a city located in the dust export pathway off the west coast of North Africa, using air-quality observations from a six-year period (2012−2017). During winter intense dust outbreaks PM<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>10</mn> </msub> </semantics> </math> </inline-formula> mean (24-h) concentrations increased from 14 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math> </inline-formula>g m<inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics> </math> </inline-formula> to 98 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math> </inline-formula>g m<inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics> </math> </inline-formula>, on average, and PM<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mrow> <mn>2</mn> <mo>.</mo> <mn>5</mn> </mrow> </msub> </semantics> </math> </inline-formula> mean (24-h) concentrations increased from 6 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math> </inline-formula>g m<inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics> </math> </inline-formula> to 32 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">μ</mi> </semantics> </math> </inline-formula>g m<inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics> </math> </inline-formula>. Increases were less during summer outbreaks, with a tripling of PM<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>10</mn> </msub> </semantics> </math> </inline-formula> and PM<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mrow> <mn>2</mn> <mo>.</mo> <mn>5</mn> </mrow> </msub> </semantics> </math> </inline-formula> daily mean concentrations. We found that desert dust outbreaks reduced the height of the marine boundary layer in our study area by >45%, on average, in summer and by ∼25%, on average, in winter. This thinning of the marine boundary layer was associated with an increase of local anthropogenic pollution during dust outbreaks. NO<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>2</mn> </msub> </semantics> </math> </inline-formula> and NO mean concentrations more than doubled and even larger relative increases in black carbon were observed during the more intense summer dust outbreaks; increases also occurred during the winter outbreaks but were less than in summer. This has public health implications; local anthropogenic emissions need to be reduced even further in areas that are impacted by desert dust outbreaks to reduce adverse health effects.
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