This visualization displays air quality measurements for New York City boroughs, showing bar charts for PM2.5, NO2, and O3 levels. Users switch between pollutants via buttons, which update the chart title and redraw the bars. The D3 v7 code uses `d3.scaleBand` for the x-axis, `d3.scaleLinear` for the y-axis, and `d3.axisLeft`/`d3.axisBottom` for axes. Hovering over a bar reveals the value differences between that borough and all others, using D3 transitions and appended text labels.