diff --git a/pyaerocom/data/variables.ini b/pyaerocom/data/variables.ini
index 729a8d83c..93d3eeb82 100644
--- a/pyaerocom/data/variables.ini
+++ b/pyaerocom/data/variables.ini
@@ -5283,3 +5283,17 @@ minimum = -150
 maximum = 150
 dimensions = time,lev,station
 comments_and_purpose = For physics evaluation and chemistry interpretation above stations' locations.
+
+[ratpm10pm25]
+description = ratio of pm10 and pm25
+unit = 1
+minimum = -150
+maximum = 150
+dimensions = time,lat,lon
+
+[ratpm25pm10]
+description = ratio of pm25 and pm10
+unit = 1
+minimum = -150
+maximum = 150
+dimensions = time,lat,lon
diff --git a/pyaerocom/ungriddeddata.py b/pyaerocom/ungriddeddata.py
index 793a9c1d3..20ad89550 100644
--- a/pyaerocom/ungriddeddata.py
+++ b/pyaerocom/ungriddeddata.py
@@ -1230,7 +1230,12 @@ def to_station_data_all(
                 out_data["stats"].append(data)
 
             # catch the exceptions that are acceptable
-            except (VarNotAvailableError, TimeMatchError, DataCoverageError) as e:
+            except (
+                VarNotAvailableError,
+                TimeMatchError,
+                DataCoverageError,
+                NotImplementedError,
+            ) as e:
                 logger.warning(f"Failed to convert to StationData Error: {repr(e)}")
                 out_data["failed"].append([idx, repr(e)])
         return out_data
diff --git a/pyaerocom/units_helpers.py b/pyaerocom/units_helpers.py
index 119fae2c7..b17be3f03 100644
--- a/pyaerocom/units_helpers.py
+++ b/pyaerocom/units_helpers.py
@@ -48,6 +48,10 @@
         ["concoa", "ug C/m3", "ug m-3", 1.0],
         ["concoc", "ug C/m3", "ug m-3", 1.0],
         ["conctc", "ug C/m3", "ug m-3", 1.0],
+        # a little hacky for ratpm10pm25...
+        # ["ratpm10pm25", "ug m-3", "1", 1.0],
+        ["concpm25", "ug m-3", "1", 1.0],
+        ["concpm10", "ug m-3", "1", 1.0],
         ["concno2", "ug N/m3", "ug m-3", M_NO2 / M_N],
         # ["concno3", "ug N/m3", "ug m-3", M_NO3 / M_N],
         ["concnh3", "ug N/m3", "ug m-3", M_NH3 / M_N],
diff --git a/tests/test_units_helpers.py b/tests/test_units_helpers.py
index 8b00433b7..cac3729b4 100644
--- a/tests/test_units_helpers.py
+++ b/tests/test_units_helpers.py
@@ -55,6 +55,8 @@ def test__unit_conversion_fac_si(from_unit: str, to_unit: str, result: float):
         ("concbc", "ug C/m3", "ug m-3", 1),
         ("concoa", "ug C/m3", "ug m-3", 1),
         ("concoc", "ug C/m3", "ug m-3", 1),
+        ("concpm25", "ug m-3", "1", 1),
+        ("concpm10", "ug m-3", "1", 1),
         ("wetso4", "kg S/ha", "kg m-2", 0.0003),
         ("concso4pr", "mg S/L", "g m-3", 2.995821),
     ],