Large dust outbreak threatens the respiratory health of more than 100 million over next 10 days

Over the next few days, large quantities of millions of pounds of dust from the Sahara desert will enter into Nigeria, Benin, Ghana, Togo and Cote d-Ivorie.   It will pose a serious health hazard to more than 100 million in this region, especially those with existing respiratory disease, the young and elderly.   While this may seem like the typical garden variety type of dust event it is not.  Why????

1.  Duration.  This event is expected to last at least 5 days followed by another dust event.

2.  Intensity.  Dust levels will reach hazardous levels

3.  Scale.  The dust will cover thousands of miles and impact large cities such as Lagos (18 million), Ibadan, Cotonou, Accra and Kumasi.  Additional dust sites will be activated and impact Niamey and eventually Ouagadougou, Bamako and Dakar.

4. Health Impacts.  Based on what we have seen this year, the dust particles are PM2.5 which is about 25 times smaller than a human hair.  These particles reach deep into the lung system causing problems for those who have COPD, Asthma or other respiratory problems.

5. Prior Exposure.  Most Guinea locations in Nigeria, Ghana, Togo, Benin and Cote d'Ivoire have experienced many hours of bad air quality since December.  The negative health effects are likely
evident even if not well reported.

What is at the root of this event and the earlier ones. 

Positive Phase of the North Atlantic Oscillation (NAO) - which yields a strong Azores high that migrates into North Africa.  This year, the NAO has been locked in a positive phase leading to dust transport across most of West Africa.

Depiction of Azores high moving over North Africa and transporting dust 

The positive NAO has also been responsible for very warm temperatures across Europe this winter.

washingtonpost.com/weather/2020/02/03/warmth-is-really-unheard-much-eastern-europe-including-helsinki-moscow-saw-warmest-january-record/


Over the next 14 days, the area of high pressure is expected remain strong as depicted in the GFS model for 72 hours.   This pattern will send dust from Chad into Nigeria.

GFS Sunday morning (Feb 9) forecast of sea level pressure and Anomaly. Red represents higher than normal pressure

This pattern is forecasted to persist over North Africa as shown by the ECMWF model for next Wednesday, Feb 12

ECMWF Wednesday (Feb 11, 2020) Afternoon forecast of sea level pressure and anomalies.

What this means, is that dust will continue to flow strongly from Chad into the Guinea coast and westward toward Niger, Mali and Senegal.  I have run the WRF regional model with dust and the forecast from Wednesday depicts lots 

of dust moving first into Nigeria tomorrow but eventually making its way across much of West Africa.  The model underpredicts the amounts of dust coming into locations like Accra, Lagos and Abidjan and these values will be much higher than shown.

Caption:  WRF depiction of PM10 dust concentration on Sat Feb 8 and Tuesday, Feb 11 2020.

Those colors in orange or red represent hazard dust levels and as a short term hazard represent a certain level of mortality (> 12 %).  By reference, the World Health Organization (WHO) recommends no more than 50 microgram per meter cubed in a 24 hour period.  It is likely that people will see 4-10 times this amount and for the smallest particles of PM2.5 will see greater 50 micrograms per meter cubed;  WHO recommends no more than 25 50 microgram per meter cubed in a 24 hour period.   Because the exposure may be significant it is recommended that 

1. Limit outdoor activity 

2. Close windows 

3.  Monitor the young, elderly and those with existing respiratory conditions

4.  WEAR a mask if you have one.

5.  Go to the hospital if you are feeling acute symptoms such as shortness of breath or chest pains.