California Cities Ranked by Indoor Radon Levels

Measured averages from Airthings devices across California, USA. Action level: 4 pCi/L — the threshold at which remediation is recommended.

Lake Arrowhead has the highest measured indoor radon in California at 7.6 pCi/L, based on Airthings measurements across 365 cities.

Updated August 30, 2026

Highest city

7.6pCi/L

Lake Arrowhead

California city average

1.1pCi/L

across 365 cities

Above action level

5/ 365

cities

California Cities Ranked by Indoor Radon Levels
#	Location	Avg level	vs action level
1	Lake Arrowhead	7.6 pCi/L	1.9× over
2	Mammoth Lakes	6.3 pCi/L	1.6× over
3	Deer Park	5.9 pCi/L	1.5× over
4	Echo Park	5.6 pCi/L	1.4× over
5	Alta Sierra	4.6 pCi/L	1.2× over
✓ Below EPA action level (4 pCi/L)
6	Atascadero	3.7 pCi/L	0.9× under
7	South Lake Tahoe	3.5 pCi/L	0.9× under
8	Pomona	3.5 pCi/L	0.9× under
9	West Hills	3.5 pCi/L	0.9× under
10	Fairfield	3.1 pCi/L	0.8× under
11	Brea	3.1 pCi/L	0.8× under
12	Mission Canyon	3.1 pCi/L	0.8× under
13	La Habra Heights	3.0 pCi/L	0.7× under
14	East Palo Alto	2.9 pCi/L	0.7× under
15	Alameda	2.8 pCi/L	0.7× under
16	Truckee	2.8 pCi/L	0.7× under
17	Grass Valley	2.8 pCi/L	0.7× under
18	Palos Verdes Estates	2.8 pCi/L	0.7× under
19	Dollar Point	2.7 pCi/L	0.7× under
20	Woodland Hills	2.7 pCi/L	0.7× under
21	Oildale	2.6 pCi/L	0.7× under
22	Sunnyside-Tahoe City	2.6 pCi/L	0.7× under
23	East Oakdale	2.5 pCi/L	0.6× under
24	Nevada City	2.5 pCi/L	0.6× under
25	Hayward	2.4 pCi/L	0.6× under
26	Los Gatos	2.3 pCi/L	0.6× under
27	Twain Harte	2.3 pCi/L	0.6× under
28	Lexington Hills	2.3 pCi/L	0.6× under
29	Portola Valley	2.2 pCi/L	0.6× under
30	Calabasas	2.2 pCi/L	0.6× under
31	Kings Beach	2.2 pCi/L	0.6× under
32	Tahoe Vista	2.2 pCi/L	0.6× under
33	Hidden Hills	2.2 pCi/L	0.6× under
34	Lathrop	2.2 pCi/L	0.6× under
35	Rancho Palos Verdes	2.2 pCi/L	0.6× under
36	Scotts Valley	2.1 pCi/L	0.5× under
37	Sherman Oaks	2.1 pCi/L	0.5× under
38	Westlake Village	2.1 pCi/L	0.5× under
39	Felton	2.1 pCi/L	0.5× under
40	Tahoma	2.1 pCi/L	0.5× under
41	Minkler	2.1 pCi/L	0.5× under
42	Fresno	2.1 pCi/L	0.5× under
43	Simi Valley	2.0 pCi/L	0.5× under
44	Montecito	2.0 pCi/L	0.5× under
45	Arnold	2.0 pCi/L	0.5× under
46	Boulder Creek	2.0 pCi/L	0.5× under
47	Agoura	1.9 pCi/L	0.5× under
48	Ramona	1.9 pCi/L	0.5× under
49	Saratoga	1.9 pCi/L	0.5× under
50	Woodside	1.8 pCi/L	0.5× under
51	Pasatiempo	1.8 pCi/L	0.5× under
52	Villa Park	1.8 pCi/L	0.5× under
53	Summerland	1.8 pCi/L	0.4× under
54	North Fair Oaks	1.7 pCi/L	0.4× under
55	Isla Vista	1.7 pCi/L	0.4× under
56	Loyola	1.7 pCi/L	0.4× under
57	Ojai	1.7 pCi/L	0.4× under
58	Universal City	1.7 pCi/L	0.4× under
59	San Pedro	1.7 pCi/L	0.4× under
60	La Habra	1.6 pCi/L	0.4× under
61	Santa Susana	1.6 pCi/L	0.4× under
62	Northridge	1.6 pCi/L	0.4× under
63	Fair Oaks	1.6 pCi/L	0.4× under
64	Menlo Park	1.6 pCi/L	0.4× under
65	Modesto	1.5 pCi/L	0.4× under
66	Laguna	1.5 pCi/L	0.4× under
67	Culver City	1.5 pCi/L	0.4× under
68	Buena Vista	1.5 pCi/L	0.4× under
69	Chico	1.5 pCi/L	0.4× under
70	Emeryville	1.5 pCi/L	0.4× under
71	Orinda	1.5 pCi/L	0.4× under
72	Palo Alto	1.5 pCi/L	0.4× under
73	Alturas	1.4 pCi/L	0.4× under
74	East Richmond Heights	1.4 pCi/L	0.4× under
75	Palm Springs	1.4 pCi/L	0.4× under
76	Parkway	1.4 pCi/L	0.4× under
77	Santa Barbara	1.4 pCi/L	0.4× under
78	Alamo	1.4 pCi/L	0.4× under
79	Corona	1.4 pCi/L	0.3× under
80	Indio	1.3 pCi/L	0.3× under
81	Rolling Hills Estates	1.3 pCi/L	0.3× under
82	Agoura Hills	1.3 pCi/L	0.3× under
83	Malibu Beach	1.3 pCi/L	0.3× under
84	Mount Hermon	1.3 pCi/L	0.3× under
85	Sleepy Hollow	1.3 pCi/L	0.3× under
86	Mission Viejo	1.3 pCi/L	0.3× under
87	Sunnyvale	1.3 pCi/L	0.3× under
88	Visalia	1.3 pCi/L	0.3× under
89	Canoga Park	1.3 pCi/L	0.3× under
90	Davis	1.3 pCi/L	0.3× under
91	Fullerton	1.3 pCi/L	0.3× under
92	Brentwood	1.3 pCi/L	0.3× under
93	Atherton	1.3 pCi/L	0.3× under
94	Chino Hills	1.2 pCi/L	0.3× under
95	East Foothills	1.2 pCi/L	0.3× under
96	Empire	1.2 pCi/L	0.3× under
97	Gold River	1.2 pCi/L	0.3× under
98	Pleasant Hill	1.2 pCi/L	0.3× under
99	Los Altos Hills	1.2 pCi/L	0.3× under
100	North Hollywood	1.2 pCi/L	0.3× under
101	Placentia	1.2 pCi/L	0.3× under
102	Monterey Park	1.2 pCi/L	0.3× under
103	Campbell	1.2 pCi/L	0.3× under
104	Los Altos	1.2 pCi/L	0.3× under
105	Piedmont	1.2 pCi/L	0.3× under
106	Vineyard	1.2 pCi/L	0.3× under
107	Carmel Valley Village	1.1 pCi/L	0.3× under
108	Newark	1.1 pCi/L	0.3× under
109	Altadena	1.1 pCi/L	0.3× under
110	Rolling Hills	1.1 pCi/L	0.3× under
111	Anaheim	1.1 pCi/L	0.3× under
112	Concord	1.1 pCi/L	0.3× under
113	Redwood City	1.1 pCi/L	0.3× under
114	West Menlo Park	1.1 pCi/L	0.3× under
115	Glendale	1.1 pCi/L	0.3× under
116	Kensington	1.1 pCi/L	0.3× under
117	Lincoln Village	1.1 pCi/L	0.3× under
118	Oceanside	1.1 pCi/L	0.3× under
119	Salinas	1.1 pCi/L	0.3× under
120	Castro Valley	1.0 pCi/L	0.3× under
121	Corte Madera	1.0 pCi/L	0.3× under
122	Goleta	1.0 pCi/L	0.3× under
123	Malibu	1.0 pCi/L	0.3× under
124	Topanga	1.0 pCi/L	0.3× under
125	East Pasadena	1.0 pCi/L	0.3× under
126	Poway	1.0 pCi/L	0.3× under
127	Van Nuys	1.0 pCi/L	0.3× under
128	Carmel-by-the-Sea	1.0 pCi/L	0.3× under
129	Danville	1.0 pCi/L	0.3× under
130	Hacienda Heights	1.0 pCi/L	0.3× under
131	Orangevale	1.0 pCi/L	0.3× under
132	Santa Clara	1.0 pCi/L	0.3× under
133	Walnut	1.0 pCi/L	0.3× under
134	Casa de Oro-Mount Helix	1.0 pCi/L	0.2× under
135	Belvedere	1.0 pCi/L	0.2× under
136	Cupertino	1.0 pCi/L	0.2× under
137	Los Serranos	1.0 pCi/L	0.2× under
138	Clovis	0.9 pCi/L	0.2× under
139	Elk Grove	0.9 pCi/L	0.2× under
140	Emerald Lake Hills	0.9 pCi/L	0.2× under
141	Oak Park	0.9 pCi/L	0.2× under
142	Hollywood	0.9 pCi/L	0.2× under
143	Yountville	0.9 pCi/L	0.2× under
144	South Pasadena	0.9 pCi/L	0.2× under
145	Walnut Creek	0.9 pCi/L	0.2× under
146	Century City	0.9 pCi/L	0.2× under
147	Chatsworth	0.9 pCi/L	0.2× under
148	Ladera	0.9 pCi/L	0.2× under
149	Santa Monica	0.9 pCi/L	0.2× under
150	Santa Venetia	0.9 pCi/L	0.2× under
151	Home Gardens	0.9 pCi/L	0.2× under
152	Sacramento	0.9 pCi/L	0.2× under
153	San Luis Obispo	0.9 pCi/L	0.2× under
154	Tustin	0.9 pCi/L	0.2× under
155	Ventura	0.9 pCi/L	0.2× under
156	Westwood, Los Angeles	0.9 pCi/L	0.2× under
157	Tracy	0.9 pCi/L	0.2× under
158	San Anselmo	0.9 pCi/L	0.2× under
159	San Marino	0.9 pCi/L	0.2× under
160	Woodland	0.9 pCi/L	0.2× under
161	Monte Sereno	0.8 pCi/L	0.2× under
162	Moraga	0.8 pCi/L	0.2× under
163	Mountain View	0.8 pCi/L	0.2× under
164	San Juan Capistrano	0.8 pCi/L	0.2× under
165	Cambrian Park	0.8 pCi/L	0.2× under
166	Highlands-Baywood Park	0.8 pCi/L	0.2× under
167	Camarillo	0.8 pCi/L	0.2× under
168	Novato	0.8 pCi/L	0.2× under
169	Saranap	0.8 pCi/L	0.2× under
170	Bonsall	0.8 pCi/L	0.2× under
171	Silver Lake	0.8 pCi/L	0.2× under
172	Yorba Linda	0.8 pCi/L	0.2× under
173	Diamond Bar	0.8 pCi/L	0.2× under
174	Fairbanks Ranch	0.8 pCi/L	0.2× under
175	Thousand Oaks	0.8 pCi/L	0.2× under
176	Beverly Hills	0.8 pCi/L	0.2× under
177	Burbank	0.8 pCi/L	0.2× under
178	Fontana	0.8 pCi/L	0.2× under
179	Fairfax	0.8 pCi/L	0.2× under
180	Fremont	0.8 pCi/L	0.2× under
181	Rancho Santa Fe	0.8 pCi/L	0.2× under
182	Fairview	0.8 pCi/L	0.2× under
183	Sausalito	0.8 pCi/L	0.2× under
184	Carmichael	0.8 pCi/L	0.2× under
185	Folsom	0.8 pCi/L	0.2× under
186	Lafayette	0.8 pCi/L	0.2× under
187	Seven Trees	0.8 pCi/L	0.2× under
188	Moorpark	0.8 pCi/L	0.2× under
189	Murrieta Hot Springs	0.8 pCi/L	0.2× under
190	Westminster	0.8 pCi/L	0.2× under
191	Belmont	0.7 pCi/L	0.2× under
192	El Cerrito	0.7 pCi/L	0.2× under
193	La Crescenta-Montrose	0.7 pCi/L	0.2× under
194	Los Angeles	0.7 pCi/L	0.2× under
195	Albany	0.7 pCi/L	0.2× under
196	Gilroy	0.7 pCi/L	0.2× under
197	Lomita	0.7 pCi/L	0.2× under
198	Redlands	0.7 pCi/L	0.2× under
199	Stanford	0.7 pCi/L	0.2× under
200	Union City	0.7 pCi/L	0.2× under
201	Berkeley	0.7 pCi/L	0.2× under
202	Rocklin	0.7 pCi/L	0.2× under
203	San Carlos	0.7 pCi/L	0.2× under
204	Brisbane	0.7 pCi/L	0.2× under
205	Burlingame	0.7 pCi/L	0.2× under
206	Marina del Rey	0.7 pCi/L	0.2× under
207	Pasadena	0.7 pCi/L	0.2× under
208	San Leandro	0.7 pCi/L	0.2× under
209	Oxnard	0.7 pCi/L	0.2× under
210	Rowland Heights	0.7 pCi/L	0.2× under
211	San Fernando	0.7 pCi/L	0.2× under
212	Benicia	0.7 pCi/L	0.2× under
213	Roseville	0.7 pCi/L	0.2× under
214	San Gabriel	0.7 pCi/L	0.2× under
215	Sebastopol	0.7 pCi/L	0.2× under
216	Alum Rock	0.7 pCi/L	0.2× under
217	Del Mar	0.7 pCi/L	0.2× under
218	El Sobrante	0.7 pCi/L	0.2× under
219	Las Flores	0.7 pCi/L	0.2× under
220	Rancho Mirage	0.7 pCi/L	0.2× under
221	Clayton	0.7 pCi/L	0.2× under
222	East San Gabriel	0.7 pCi/L	0.2× under
223	Hermosa Beach	0.7 pCi/L	0.2× under
224	San Marcos	0.7 pCi/L	0.2× under
225	Santa Ana	0.7 pCi/L	0.2× under
226	Alondra Park	0.7 pCi/L	0.2× under
227	Aptos	0.7 pCi/L	0.2× under
228	Escondido	0.7 pCi/L	0.2× under
229	Ladera Heights	0.7 pCi/L	0.2× under
230	Ladera Ranch	0.7 pCi/L	0.2× under
231	Lucas Valley-Marinwood	0.7 pCi/L	0.2× under
232	San Joaquin Hills	0.7 pCi/L	0.2× under
233	Carlsbad	0.6 pCi/L	0.2× under
234	Morongo Valley	0.6 pCi/L	0.2× under
235	Valley Center	0.6 pCi/L	0.2× under
236	Del Aire	0.6 pCi/L	0.2× under
237	Inglewood	0.6 pCi/L	0.2× under
238	La Mesa	0.6 pCi/L	0.2× under
239	Morgan Hill	0.6 pCi/L	0.2× under
240	North Tustin	0.6 pCi/L	0.2× under
241	Woodcrest	0.6 pCi/L	0.2× under
242	Mill Valley	0.6 pCi/L	0.2× under
243	Oxnard Shores	0.6 pCi/L	0.2× under
244	San Rafael	0.6 pCi/L	0.2× under
245	San Jose	0.6 pCi/L	0.2× under
246	San Ramon	0.6 pCi/L	0.2× under
247	West Hollywood	0.6 pCi/L	0.2× under
248	Alhambra	0.6 pCi/L	0.1× under
249	El Granada	0.6 pCi/L	0.1× under
250	Lincoln	0.6 pCi/L	0.1× under
251	Livermore	0.6 pCi/L	0.1× under
252	Portola Hills	0.6 pCi/L	0.1× under
253	Saticoy	0.6 pCi/L	0.1× under
254	View Park-Windsor Hills	0.6 pCi/L	0.1× under
255	Daly City	0.6 pCi/L	0.1× under
256	La Canada Flintridge	0.6 pCi/L	0.1× under
257	La Jolla	0.6 pCi/L	0.1× under
258	Laguna Beach	0.6 pCi/L	0.1× under
259	Laguna Niguel	0.6 pCi/L	0.1× under
260	Laguna Woods	0.6 pCi/L	0.1× under
261	Cerritos	0.6 pCi/L	0.1× under
262	Indian Wells	0.6 pCi/L	0.1× under
263	Milpitas	0.6 pCi/L	0.1× under
264	San Diego	0.6 pCi/L	0.1× under
265	Santa Cruz	0.6 pCi/L	0.1× under
266	West Sacramento	0.6 pCi/L	0.1× under
267	El Cajon	0.6 pCi/L	0.1× under
268	San Mateo	0.6 pCi/L	0.1× under
269	Temple City	0.6 pCi/L	0.1× under
270	Vallejo	0.6 pCi/L	0.1× under
271	Foothill Ranch	0.6 pCi/L	0.1× under
272	Hillsborough	0.6 pCi/L	0.1× under
273	Stanton	0.6 pCi/L	0.1× under
274	Antelope	0.6 pCi/L	0.1× under
275	Pleasanton	0.5 pCi/L	0.1× under
276	San Clemente	0.5 pCi/L	0.1× under
277	Blackhawk	0.5 pCi/L	0.1× under
278	Lake Forest	0.5 pCi/L	0.1× under
279	Aliso Viejo	0.5 pCi/L	0.1× under
280	Encinitas	0.5 pCi/L	0.1× under
281	Rossmoor	0.5 pCi/L	0.1× under
282	Trabuco Canyon	0.5 pCi/L	0.1× under
283	Boyle Heights	0.5 pCi/L	0.1× under
284	Dublin	0.5 pCi/L	0.1× under
285	Irvine	0.5 pCi/L	0.1× under
286	Lake San Marcos	0.5 pCi/L	0.1× under
287	Napa	0.5 pCi/L	0.1× under
288	Vacaville	0.5 pCi/L	0.1× under
289	Waldon	0.5 pCi/L	0.1× under
290	East La Mirada	0.5 pCi/L	0.1× under
291	El Rio	0.5 pCi/L	0.1× under
292	Oakland	0.5 pCi/L	0.1× under
293	San Francisco	0.5 pCi/L	0.1× under
294	Ashland	0.5 pCi/L	0.1× under
295	Monrovia	0.5 pCi/L	0.1× under
296	Tamalpais-Homestead Valley	0.5 pCi/L	0.1× under
297	El Dorado Hills	0.5 pCi/L	0.1× under
298	Larkfield-Wikiup	0.5 pCi/L	0.1× under
299	Richmond	0.5 pCi/L	0.1× under
300	San Antonio Heights	0.5 pCi/L	0.1× under
301	Healdsburg	0.5 pCi/L	0.1× under
302	Mira Loma	0.5 pCi/L	0.1× under
303	Torrance	0.5 pCi/L	0.1× under
304	Colma	0.5 pCi/L	0.1× under
305	Huntington Beach	0.5 pCi/L	0.1× under
306	Redondo Beach	0.5 pCi/L	0.1× under
307	Sierra Madre	0.5 pCi/L	0.1× under
308	Windsor	0.5 pCi/L	0.1× under
309	Cameron Park	0.4 pCi/L	0.1× under
310	Del Rey Oaks	0.4 pCi/L	0.1× under
311	Los Alamitos	0.4 pCi/L	0.1× under
312	Rancho Cucamonga	0.4 pCi/L	0.1× under
313	Santa Rosa	0.4 pCi/L	0.1× under
314	Strawberry	0.4 pCi/L	0.1× under
315	Casa Conejo	0.4 pCi/L	0.1× under
316	Buena Park	0.4 pCi/L	0.1× under
317	Orcutt	0.4 pCi/L	0.1× under
318	Lemon Grove	0.4 pCi/L	0.1× under
319	Vista	0.4 pCi/L	0.1× under
320	Claremont	0.4 pCi/L	0.1× under
321	Gardena	0.4 pCi/L	0.1× under
322	Arden-Arcade	0.4 pCi/L	0.1× under
323	Chino	0.4 pCi/L	0.1× under
324	Costa Mesa	0.4 pCi/L	0.1× under
325	El Segundo	0.4 pCi/L	0.1× under
326	Mayflower Village	0.4 pCi/L	0.1× under
327	Santa Clarita	0.4 pCi/L	0.1× under
328	Coronado	0.4 pCi/L	0.1× under
329	Temecula	0.4 pCi/L	0.1× under
330	Fountain Valley	0.4 pCi/L	0.1× under
331	Seacliff	0.4 pCi/L	0.1× under
332	Midway City	0.4 pCi/L	0.1× under
333	Pacifica	0.4 pCi/L	0.1× under
334	Redwood Shores	0.4 pCi/L	0.1× under
335	La Mirada	0.3 pCi/L	0.1× under
336	Manhattan Beach	0.3 pCi/L	0.1× under
337	National City	0.3 pCi/L	0.1× under
338	Norco	0.3 pCi/L	0.1× under
339	Hawaiian Gardens	0.3 pCi/L	0.1× under
340	Millbrae	0.3 pCi/L	0.1× under
341	Long Beach	0.3 pCi/L	0.1× under
342	Yucaipa	0.3 pCi/L	0.1× under
343	Lakewood	0.3 pCi/L	0.1× under
344	Orange	0.3 pCi/L	0.1× under
345	Palm Desert	0.3 pCi/L	0.1× under
346	Signal Hill	0.3 pCi/L	0.1× under
347	La Palma	0.3 pCi/L	0.1× under
348	North Glendale	0.3 pCi/L	0.1× under
349	Petaluma	0.3 pCi/L	0.1× under
350	South San Francisco	0.3 pCi/L	0.1× under
351	Valencia	0.3 pCi/L	0.1× under
352	Lawndale	0.3 pCi/L	0.1× under
353	Pacific Grove	0.3 pCi/L	0.1× under
354	Arcadia	0.3 pCi/L	0.1× under
355	Granite Bay	0.3 pCi/L	0.1× under
356	Opal Cliffs	0.3 pCi/L	0.1× under
357	Cypress	0.3 pCi/L	0.1× under
358	Lompoc	0.3 pCi/L	0.1× under
359	Seal Beach	0.3 pCi/L	0.1× under
360	Bonita	0.3 pCi/L	0.1× under
361	Broadmoor	0.3 pCi/L	0.1× under
362	Newport Beach	0.3 pCi/L	0.1× under
363	Foster City	0.2 pCi/L	0.1× under
364	Santa Fe Springs	0.2 pCi/L	0.1× under
365	San Lorenzo	0.2 pCi/L	0.1× under

See USA cities ranked by radon level See all States ranked by radon level