Elemental Affinity (in humans)

Attunement to elemental planes is a property of physical matter, driven by red quanta. When significant portions of a living entity are attuned to certain elements, they have affinity for the given plane. This is similar to, but not necessarily directly linked to, their Patterns of Life.

Fire

Fire affinity is a bit of a weird one. Its most obvious trait is relatively simple- an incredible resistance to change in temperature.
Look a bit deeper, and there are some stranger things. For example, the ability to ignore the negative effects of smoke on breathing (not on vision, mind you). This implies several things, such as the ability to breathe (ie extract oxygen) in smoke, and a lack of tar buildup in the lungs. The simple answer to this is dimensional fuckery aiding the observer effect. Dimensional affinities in general can allow internal bits to be shunted to other planes through the observer effect- this allows for the filtration of smoke (and also Cotd eyes, but that's another topic).
Having a high fire affinity changes the mechanism of aging.

Aging

Fire affinity visually creates ember-like effects across one's body. Such markings often manifest in patterns reminiscent of wrinkles or cracking (see: ashen one in DS3). Once these appear, they spread like a cancer, dramatically increasing one's soul flow along the way. The process can be slowed by excessive drinking, which of course creates its own problems. Once they start glowing and spreading, the individual typically has less than two years to live. Roughly speaking, any time spent drunk will not contribute to this countdown. It will lead to liver failure, though.
Technically speaking, such markings can occur at any point in one's lifespan, though it becomes more likely as time goes on. It's almost guaranteed by the age of 60. Think of it as fire-based cancer; it's simply an inevitability which goes with the territory of controlling Fire. Things like dragons are built from the ground up to be aligned with Fire, and literally grow to contain it. Human biology isn't so flexible- though interestingly, if the ember onset begins in adolescence, the person can grow along with the fire instead of being consumed by it.
Note that the described effects are related to a very high affinity for fire. Somebody who only consumes a shard or two during the glass-eating ritual will experience none of these, but basically every midland noble line has orders of magnitude more than that within them.

Blood

An 'affinity' for blood generally translates into affinity for Xiphaem.
Along with this is having more blood than should really fit in one's body. This is a result of the affinity instinctively drawing material from the plane. Interestingly, this only occurs in humans- ghouls don't directly draw from Blood at all.
Blood type matters. The sea in Blood is AB+, so only those with AB+ blood can draw on it without poisoning themselves. While a strong affinity for Blood will power through ABO incompatibility reactions, it's still added discomfort, distraction, and drain on efficiency. About 10% of Wastelanders are AB+. Having such a blood type is heavily correlated with success due to the xiphaem-focused culture of the region.

Mixed Affinity

Generally speaking, mixing affinities results in some sort of composition between the two's effects. In other cases, it can result in an insulative effect against any dimensional magic.
What makes Blood rather dangerous is its long history of messily changing hands. Drawing upon Blood itself is relatively predictable in the modern (post-Chaos) era due to the benign (more uninterested, really) nature of its sovereign. However, accessing Blood-adjacent parts of dimensional space is incredibly risky, as one can easily unearth the works of any number of previous rulers of Blood, most of which have historically been far more malevolent.

Storms

Storms affinity tends to divert flubbing towards preventing mental damage. This consequently results in faster physical deterioration (that is, mundane physical deterioration instead of magically slowed by internal flubbing), while essentially halting any mental deterioration. This is something of an inverse to Darkness, which preserves the body while not having any additional effects on the mind (though the nature of consciousness and the soul mean that mundane senility in something Darkness-aligned enough for this to be measurable is rare regardless).

Darkness

Darkness affinity simply prevents aging. There's an inherent stasis/stability effect associated with the affinity which works on a deeper level than flubbing, actually preventing and healing damage instead of simply compensating for it. This effect is rather easy to steal from another, meaning that though technically capable of living indefinitely, most Darkness-aligned end up subsumed by greater things before even a typical lifespan. The exception to this occurs in the lunar races, bound by Vhagar to not kill one another.