Silca Airs and Hang Gliding Sites?
http://www.worldhangglidingassociation.org/SilicaAirs.html is this page
Similar question should be asked about any hang gliding site on Earth.
In general: know what one is breathing at a hang gliding site. What is upwind?
by Joe Faust
Why I am not going to recreate at hang gliding at a particular site Dockweiler Hang Gliding Park anymore: 

I've correlated an important set of symptoms with sessions of long play in the wind at Dockweiler Hang Gliding Park.

The vector suspected:   respirable silica  
The wind is wanted.  The wind comes off the ocean and wafts over a long stretch of sand.   I grew up playing at the surf zone at Venice Beach and in the surf; no problem. But I did not grow up playing at the leeward end of the sand: problem therein. And playing at the leeward end of the sand for six to 10 hours sessions exercising hard hang gliding: this is a new deal. And it seems now that the new deal has brought the beginnings of lung disease. The suspect will be described below. 

The sand has high content of silica. The sand is ground finer and finer by these actions:
  • Large sand-sifting vehicles used by the County to sift trash from the sand inadvetently crush and grind sand particles against each other to form finer and finer particulates of silica. These big vehicles are used on a frequent regular basis to keep the beach sand clean.
  • Thousands of people walking over the sand regularly crush and grind sand against itself.
  • My shoes at each flight returning walk-wing-carry grind the sand to finer silica particles.
  • Police cars drive on drier run of the beach sand only to crush and grind the sand finer.
  • Emergency trucks drive on the drier run of the beach sand.
  • Junior lifeguards have regular running on the dry sand to grind sand to finer particulates.
  • Wind tumbles the sand to abrade the sand to finer particulates.
The flocks of seagulls poop on the sand; calculate unending tons of poop being mixed with the sand; each bird resting and pooping near the shoreline; that poop gets into the sand and eventually feeds microbes and the wind that reaches my lungs.  The sand is heated daily. Night dew and moisture from the continuous wave breaks moisten the broad stretch of sand. Microbes grow in the moist sand just beneath the sun-soaked top layer of the sand. The wind and activity of people and machines and lifeguard vehicles continually churn the sand to grind it to finer and finer texture; and wind and activity give upwelling to the detritus of the microbes. The net result is that the wanted wind wafts over the sand and brings to the high-intensity-exercising-breathing hang glider pilot an air soup of particulates of fine order. Those fine particulates reach the lower finer levels of the lung and brings disease. 

"It only takes a very small amount of the very fine respirable silica dust to create a health hazard."  https://www.silica-safe.org

Beginning silicosis and other inflammations brings symptoms that match the symptoms that I am having on the night and days following long-hour sessions at the Dockweiler hang gliding site. Headaches, voice changing, and malaise are pointedly noticed; and such is different from what I know from long hours of work and exercises done in environments that do not have the fine particulates. 

    My thought prejudice that the "beach" was a place of health has been altered. 

I still believe that the wave-area of the wind-receiving beach and the water place for playing, running, standing to fly kites, swimming, surfing, etc. brings good airs to the lungs.  But the leeward end of the broad sand is now something that deepens lung injury.  I am not going to play again at the leeward end of broad beaches, but only at the wave-area windward side of onshore-breeze-swept beaches. That means that Dockweiler hang gliding for me is permanently a no-more item of my life. A new normal has arrived.  I will hang glide only at other sites that do not present such a health challenge. This is a big change for me. 

"Normal sand is not Silica sand. Though normal sand composition consists of silica(Si02) it is not 100% silica."


     Will I be willing to wear a fine-particulate filter​-based ​​ respirator in order to have long sessions of exercise via hang gliding at the Dockweiler site?  Don't think so. ​  Rest and living do not remove the fine silica particles from the lung.

I am no longer in good conscience able to advocate doing hang gliding at the Dockweiler hang gliding park. The bad effects have accumulated; I want to avoid entering fatal silicosis and possibly fungal infections from non-silica dust.  ​I cannot wish the conditions on others. ​

"Silicosis is a lung disease. It usually happens in jobs where you breathe in dust that contains silica. That's a tiny crystal found in sand, rock, or mineral ores like quartz. Over time, silica can build up in one's lungs and breathing passages. This leads to scarring that makes it hard to breathe."

​"Chronic silicosis usually takes anywhere from 20 to 45 years to develop, but even 5 to 10 years exposure time at higher concentrations can result in an accelerated version of the disease." ​

Wishful thinking or hoping that something is not so, does not change facts. 
But deliberately to want wind in face during heavy exercise should perk up critical thinking; does that wind carry things injurious to health? I have not the instruments to measure the facts at the Dockweiler bluff.  But analysis seems to point to a vector of my experienced symptoms.      ??: # of micrograms per cubic meter of air (g/m3)

​​Upon such suspicions, I found some literature that may be relevant to my experience and thinking.
​Study:
Mitigation?
  • Just after a rain while the broad beach is damp might be a time for hang gliding there. 
  • Active spraying of ocean water using wind-power sprayers to wet the full broad beach might be a mitigation method; but such operation is not likely to be done by anyone. 
  • Wearing breathing masks with correct fresh filters --respirators-- could be a means to avoid further damage. We wear helmets; maybe wearing an industrial breathing filter could become the habit.  But authorities have such respirator wearing as a last resort. The dust still gets on things that are carried to car and home.  
  • https://www.silica-safe.org/ask-a-question/faq
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3683189/
  • https://www.osha.gov/silica/Silica_Public_FAQs.pdf
  • "Workers are exposed to dust containing crystalline silica for about 8 h per day and are at the risk of developing silicosis and silico-tuberculosis.

 The death of Greg DeWolf, super instructor at Dockweiler,  might be questioned. Was his lung studied post-mortem? I watched his decline over the years. He was breathing the suspect airs for very many years five days a week for six or so hours per day. The exercise and hoped-for "good airs" might have slowly degraded his lungs via silicosis; facts are not at hand and may not have been investigated.  I sent query to Cyndia Z-K and Joe Greblo about the matter.

An effort to have the State of California or the County of Los Angeles to measure matters will be made regarding the bluffs' airs at different times of day and at different conditions.

Discuss similar matters at US Hawks forum.   HERE.