Problems from static,
I live in Arizona and static charges can be a problem and safety hazzard for many things, not just handloading.
Static electricity is the term for of an object having an excess or deficiency of electrons relative to the number of protons in the material. In a conductive object a charge will only be present on the outside surface of the object (Faraday effect). Non conductive objects can carry a net charge throughout the object, but the charge isn't necessarily uniform throughout the object. Static charges usually result from from friction or pressure which mechanically strips electrons off of the surface of one object leaving it on another. Static charges will remain until they have a path to drain away. That path may just be air, which varies in it's conductivity with humidity or though ionization such as light or charged particles (cosmic and gamma ray rays which are always present.
How does that relate to handloading? We've all walked across a carpet and touched a doorknob and seen a spark. They soles of shoes (rubber or synthetics) rubbing on carpet (typically nylon) can transfer a charge to the human body. Any conductive object (like a human) has capacitance and can store a charge if it's electrically insulated. Many carpets and shoe soles are also good insulators. The voltage gnerated by shoes on nylon can be several thousand volts which can break down (ionize) a few millimeters of air with enough energy to emit visible spark and cause minor pain when some part of the body comes near a grounded object (like a door knob) . So what happens if after walking across the room you touch an open pan of powder and that spark jumps though the powder to the pan? There's a good chance it will ignite and potentially cause a burn to your fingers. If it's a lot of powder, like a pound can, it could cause severe injury or death. A wool sweater rubbed against a plastic chair can cause similar voltage and energy as you sit down or stand up.
Igniting powder is probably the worst problem static can cause a handloader. Electric sparks can initiate buring in most (all?) kinds of powder. If the powder is confined the buring is rapid and will created an explosion. Its is not a detonation, but fast enough to do real damage. It might be possible to detonate a primer with a spark, but most likey the spark will hit the metal cup and becasue of the Farady effect no current would flow through the primer material. I don't consider it a likely hazzard, but possble. It's extremely unlikely that a static dischage can set off a completed cartridge. Perhaps with Etronx primers. even then it's very unlikely.
Another problem from static charge is that any charged objects will produce a force between them. It can be attracive or repulsive. Like charges attract, unlike charges repel. The force is proportional to the total charge and the inverse square of the distance for small objects. For adjacent surfaces the force increases linearly with the voltage and area and linearly with separation for distances are short compared to the linear dimensions of the surfaces.
The good part about plastic powder handling devices is that they are unlikley to provide a conductive path from the human body to ground though powder. The problem with plastic powder handing devices (funnels, trays, spatulas, etc is that they can become charged themselves from handling or pouring powder across the surface and then the powder will tend to stick to the surface. If you've weighted powder and some of it sticks in the funnel and doesn't go into the case it can cause a drop in velocity when the cartidge is fired. If that powder comes loose from the funnel when loading the next cartrige ti could cause high velocity and possibly dangerous pressures. It would be possbible to make slightly conductive powder handing devices which could not sustain a charge for any length of time, yet would not support sparking. I haven't seen that commercially. I haven't looked for it recently either.
Scales usually have metal weighing pans but a charged object moved near a scale can cause a force which will cause inaccurate readings. In dry conditions the human body can carry a charge which can change the reading on a powder balance by many grains.
Personally I only use metal for handling powder. All of my scales, funnels, and spatulas are metal. Aluminum, brass, and stainless work equally well for static control. My loading bench is steel. I have a steel chair and both sit on a bare concrete floor which is naturally conductive so they are effectively tied together electrically. I usually wear cotton clothes which is weakly ocnductive and not bad for generating static charge. Using "anti cling" sheets when you do laundry greatly reduces the charge buildup.
Those are the same precautions used when working on semiconductor electronics, which I do for my profession and it just seems natural to take those precautions when handloading. It takes a lot less voltage to damage a CMOS gate than to ignite a powder grain. A conductive wrist strap is an added precaution used in electronics work. It ties the body to the work though a 1 megohm resistor which will drop the voltage on a body relaitve to the table to sub millivolt levels in a few milliseconds. That may be overkill for handloading but it certainly doesn't hurt and provides additonal safety.
My advice would be that if you detect any sign of static when working around your loading bench make an effort to eliminate it. A quick test is to use your powder scale to check for a static charge. Walk across the room and move the palm of your hand held flat over the pan of your scale with it held about 1/2 above the pan. If the reading canges more than .1 grain I'd work to eliminate what's causing the charge. Do the same test by sitting down on the chair you use, then stand up and move your hand over the scale. The 1/2" space from the the scale is so if you do have a large charge it's not likely to spark and damage the scale.
Two other things I can think of can generate static charges which might be around a loading bench. One is a CRT display for a computer or TV. LCDs aren't a problem. The other is a vacuum cleaner which can create a charge when particles of most materials are pulled across the interior plastic surface of the hoses. I would not use a vacuum cleaner to pick up spilled powder.
Sorry for being long winded....
