The following articles might help you. Pls find attachment. 

The exact mechanism is still unclear, although we have known for decades that welding and soldering is associated with an elevated risk of Pneumoconiosis: so-called welder's lung or welder siderosis. The physical manifestation is usually minor scattered radiological opacities probably due to uptake of minute droplets or particles of metal, but it is also associated with an elevated risk of pulmonary infection. The exposure to potentially toxic volatiles during welding or soldering may play a role. Despite the name, prolonged workplace exposure to soldering appears to generate many of the same symptoms, albeit at a lower level and is associated with asthma and wheeze.

Immunologically the affected lung seems to demonstrate chronic low level inflammation, and pneumonia in otherwise healthy welders/solderers is a known risk. It can be associated with extensive infiltration of innate immune cells, which probably contributes to immunopathology. Studies suggest that exposure to welding fumes or to solvents such as potassium aluminium tetrafluoride are associated with hyperreactivity on specific agent challenge.

I know of at least one other case of invasive aspergillosis in a welder (successfully treated by antifungals and embolization), and there have been multiple reports of pulmonary infections with organisms that are rarely encountered in healthy adults, but this still remains extremely uncommon and an underlying comorbidity can't be ruled out.

Please refer this paper

http://cid.oxfordjournals.org/content/24/4/723.full.pdf

Thank you  for the  papers and views.

Atopy and certain other subtle host immune factors alongwith the infective dose of Aspergillus  seems to be the cocktail cause of invasive aspergillosis .

I agree with all the previous suggestions and I would like to pose the possibility of CARD-9 deficiency, phagocyte oxidative burst defects and maybe also autoantibodies against IL-17 / 22.