Increase in production is not something restricted to the UK as rises in production are also reported in Mexico with detection rates also on the rise in the US.
In the face of these increases in supply and presumably use it is worth making the point again that plant material such as marijuana is an excellent food source for fungi such as Aspergillus. Once cut the material must be dried rapidly and consistently to a very low moisture level to avoid it becoming mouldy. Once dried it must be stored in completely dry conditions to prevent it becoming damp and once again quickly becoming mouldy.
Storing marijuana or any other plant material in small sealed containers or wrapped in plastic will only help if the material is completely dry in the first place, otherwise you are effectively locking the mould in with its own supply of food and water whereupon it will flourish. Mould does not need light or much heat to grow.
Once it has run out of food it will sporulate, emitting billions of tiny spores that are small enough to float on the slightest draught of air. If this material were to be wrapped up in a paper tube or placed in a pipe, one end lit and inhaled then billions of spores would very easily penetrate the lungs of the smoker to its deepest depths as they are small enough to spread to the smallest air pockets in the lungs.
Even if the smoker has a completely normal immune system it would only be able to clear so many spores in a given time. If they have any pre-existing debris or scar tissue in their lungs the spores may well be able to evade the immune system and start to grow in a similar way that the bacteria that cause tuberculosis (Tb) grow and cause cavities in the lung. Tuberculosis can be treated successfully using strong antibiotics. Deep infections by Aspergillus are far harder to eradicate and tend to become chronic infections, even with all the latest antifungal medication attacking it - the marijuana smoker is more likely to have lifelong infections that become highly debilitating.
Marijuana is a special case as it is produced and stored under a wide variety of conditions. The material you purchase is of unknown origin so its mould status is unknown. Checking its dryness on delivery is no guide to how quickly it has been dried and thus no guide to how many spores it may carry. Needless to say there is no official monitoring system controlling the quality of the supply.
Aspergillus can be black, green, brown, white, yellow or blue in colour - it is all bad and you will not necessarily be able to see it at all. Picking a few bits of mould off the material makes no difference. If you inhale in the form of a cigarette you are inhaling smoke from the burning tip through an entire tube of mouldy material - it will not be sterilised.
Breathe this material in at your own risk in full knowledge of the potential hazards.