Learn Hardcore Icelandic: Mengun hefur vond áhrif á heilsuna okkar. - Pollution has a bad effect on our health.

Mengun – pollution (a feminine noun, uncountable)
hefur – has (3rd person singular of hafa, to have)
vond – bad (adjective, here in neuter plural form)
áhrif – effects / influence / impact (neuter plural noun; literally effects)
á – on / to / onto / about; here, part of the expression hafa áhrif á e‑t = to have an effect on something
heilsuna – the health (heilsa = health, accusative singular with the definite article: the health)
okkar – our (genitive plural of við, we)

So the sentence is literally: “Pollution has bad effects on the health of us.” → “Pollution has a bad effect on our health.”

Why is hefur used here and not er? In English we just say “Pollution is bad for our health.”

Icelandic often uses the construction hafa áhrif á e‑t (to have an effect on something) where English might use simple “to be” plus an adjective.

Mengun hefur vond áhrif á heilsuna okkar.
= Pollution has bad effects on our health.

You could make a more literal parallel to English:

Mengun er slæm fyrir heilsuna okkar.
= Pollution is bad for our health.

Both are correct, but:

hafa áhrif á sounds a bit more like “to affect / to impact”,
er slæm fyrir sounds more like “is bad for”.

So hefur is used because of the idiomatic phrase hafa áhrif á, not as an auxiliary for a perfect tense here.

What exactly is áhrif? Is it singular or plural, and why is vond used like that?

Áhrif is:

a neuter plural noun in form,
but often behaves like an uncountable / mass noun in meaning: effect, influence, impact.

Grammatically, because it is neuter plural, any attributive adjective must agree:

vond áhrif – bad effects (neuter plural)
góð áhrif – good effects (neuter plural)
slæm áhrif – bad/negative effects (neuter plural)

So:

áhrif: neuter plural,
vond: neuter plural form of the adjective vondur (bad, evil),
Together: vond áhrif = “bad effects / a bad effect” in English.

What is the difference between vond and slæm here? Could I say “slæm áhrif” instead of “vond áhrif”?

Yes, you can say either:

vond áhrif
slæm áhrif

Both mean bad effects / negative effects.

Nuance:

vondur can mean bad, nasty, evil, mean. It’s common, a bit more colloquial or emotional in some contexts.
slæmur more specifically means bad, poor, harmful, of low quality. It often sounds slightly more formal or neutral in evaluations.

In a sentence about health, slæm áhrif might sound a bit more “textbook” or “scientific”, but vond áhrif is perfectly correct and perfectly natural.

Why is it “á heilsuna okkar” and not just “á heilsu okkar” or “á heilsu”?

All three patterns are possible, with slightly different nuances:

á heilsuna okkar
- heilsa
  - -na (definite article) = heilsuna (the health)
- okkar (our) after it
  → literally: on the health of us → on our health
  This sounds specific and concrete: our particular health.
á heilsu okkar
- no article on heilsa: just health
- okkar still marks it as our
  → literally: on health of us → on our health
  Also correct; many speakers would use this too. It can feel a tiny bit more abstract or generic.
á heilsu (without okkar)
- just on health or on (people’s) health in general.
  → This would mean pollution has a bad effect on health (in general), not specifically our health.

In your sentence, á heilsuna okkar emphasises our health in a definite, specific way.

Why is heilsuna in the accusative case? What does á do to the case here?

The preposition á can take either accusative or dative, depending on meaning:

á + accusative → usually motion onto / towards something, or often figuratively “acting on / affecting”
á + dative → location on something, being on top of, etc.

With hafa áhrif á e‑t (to have an effect on something), á always takes the accusative, because the idea is that something is acting upon or affecting something else.

So:

á + heilsuna (accusative singular of heilsa with article)
= on the health (as an affected object)

That’s why you have heilsuna instead of nominative heilsa or dative heilsu.

Is the word order fixed? Could I say “Mengun hefur á heilsuna okkar vond áhrif”?

In normal, neutral Icelandic word order for this kind of sentence, you would say:

Mengun hefur vond áhrif á heilsuna okkar.

The general pattern is:

Subject – Finite verb – Object / Predicate – Prepositional phrase

You could move things around for emphasis or special stylistic effect, but:

Mengun hefur á heilsuna okkar vond áhrif sounds awkward and unnatural in normal speech or writing.
It splits the verb phrase hefur … áhrif in an unusual way.

For a learner, it’s best to keep:

[Subject] Mengun
[Verb] hefur
[Object] vond áhrif
[Prep phrase] á heilsuna okkar

in that order.

What are the genders and basic forms of mengun, áhrif, and heilsa?

Briefly:

mengun – pollution
- Gender: feminine
- Typically uncountable
- Key forms (singular only, since it’s mass-like):
  - Nom: mengun
  - Acc: mengun
  - Dat: mengun
  - Gen: mengunar
áhrif – effects, influence
- Gender: neuter plural in form
- Often behaves like a mass noun
- Key forms:
  - Nom/Acc pl.: áhrif
  - Dat pl.: áhrifum
  - Gen pl.: áhrifa
heilsa – health
- Gender: feminine
- Singular:
  - Nom: heilsa
  - Acc: heilsu
  - Dat: heilsu
  - Gen: heilsu
- With definite article in accusative: heilsuna (as in the sentence)

What exactly is okkar grammatically? Is it like “our” or “ours”?

Okkar is:

the genitive plural form of the pronoun við (we),
used as a possessive: our / of us.

It works a bit like English “our” but structurally it’s more like “of us” placed after the noun:

heilsan okkar = our health (literally “the health of us”)
vinir okkar = our friends (literally “friends of us”)

So in heilsuna okkar, okkar is just marking possession: our (health).

How would I pronounce “Mengun hefur vond áhrif á heilsuna okkar”?

Approximate guide using English-like sounds (not exact IPA):

Mengun – MEHNG-oon
- ng like in English “sing” (one sound, [ŋ]); the final n is part of the same nasal sound.
hefur – HEH-vur
- h as in “hat”; e like in “bed”; f often like English v between vowels; ur is a short, unstressed “uhr”.
vond – vond (like “vont” with a d)
- o as in British “hot”; final d often softened.
áhrif – OW-rif
- á like “ow” in “cow”; hr like a slightly breathy hr sound; i like in “if”; f like f.
á – again OW in “cow”.
heilsuna – roughly HAYL-suh-na
- hei like English “hail”; lsu quickly together; final a is short, like “uh”.
okkar – OCK-ar
- stress on first syllable; kk is a strong, doubled k sound; ar like “ar” in “car” (but shorter).

Stress in Icelandic is almost always on the first syllable of each word: MEngun HEfur VOND Áhrif Á HEIlsuna OKKar.

Could I say “Mengun er slæm fyrir heilsuna okkar” instead? Is that equivalent?

Yes, that’s a very natural alternative:

Mengun er slæm fyrir heilsuna okkar.
= Pollution is bad for our health.

Differences:

hefur vond/slæm áhrif á heilsuna okkar
= has bad effects on our health → emphasises effects / impact.
er slæm fyrir heilsuna okkar
= is bad for our health → more direct assessment of pollution itself as harmful.

Both are correct; they just highlight the idea slightly differently. For everyday use, you can use either.