You have an extra " in your query:
google.maps.event.addDomListener(document.getElementById('houseChoropleth'),
'click', function() {
var houseMap = document.getElementById('houseChoropleth');
layer.setOptions({
query:{
select: "col40>>0"",
from: '16NkOpQVdCaNu8jo1Wvhk8x2LcXBXhyY4dPowkhQ'
}
});
});
}