一介の塵（ちり）を英語でなんと言うか？

一介のに相当する部分が a speck of です。0:13 what was just a speck, just 200 meters across has since grown to 2.7 square kilometers, bigger than the city state of Monaco. たった200メートルのちっぽけな岩礁が2.9キロ平米の、モナコ公国よりも大きく成長した。

Japan surveys expanding new island
https://www.youtube.com/watch?v=Lc1ZkyKwrZo  2;55 tiny specks of gold
The Philippines' child miners risking their lives for gold
https://www.youtube.com/watch?v=pqjHT8MFSow  0:30 there's not a speck of soil to be seen here at Ouroboros Farms where ...
Aquaponic farming saves water, but can it feed the country?
https://www.youtube.com/watch?v=9FlRf0StGiU  0:21 specks of fat 霜降り
Grilling steak: How to grill perfect sirloin steaks
https://www.youtube.com/watch?v=LeF7raKGYRQ  8:49 you're alone with yourself down there at depth. even your body slips away so that it feels like you're just a kind of a speck of consciousness that's floating into the abyss. この深淵でたった一人。体が追いつかなくても、魂の部分は深海を目指してさまようようなものさ。
Tanya Streeter and William Trubridge in CBS's 60 minutes

2:01 one small rock or a speck of dust, and a scratch on your camera lens could happen.

Galaxy Note 8 Durability Test!! - Scratch Burn BEND TEST!!